Muscle diseases can take different clinical aspects, and pathological features. It is important to get an accurate diagnosis of specific muscle disease. The diagnosis depends on a careful clinical history, physical exam and neurological exam. Several specialized tes:s are used to confirm a suspected diagnosis, including: muscle biopsy, enzyme histochemistry ,electron microscopic study, immunological, haematological tests and other biochemical tests. Aims of the study:- To study the clinicopathological correlation of muscle diseases by light & electron microscop correlated with the results of Electromyographical assessment, histochemical reaction of diseased skeletal muscle in addition to the haematological, biochemical, serological & immunological changes in muscle diseased patients. Subjects, Materials & Methods; This study was carried out at the Iraqi College of Medicine during the period (April 2001 to March 2002) for 72 patients with muscle diseases. Their age range was (1.8-72) years , 29 were females and 43 were male. Forty healthy subjects were Volunteers as control group with age ranged from 9-60 years. Twenty of them were females and twenty were males. This study emphasized on histopathological, histochemical(Alpha naphthyle acetate esterase and succinate dehydrogenase), ultrastructural, electromyographical(EMG), Immunological (autoantibodies), Serological (Rheumatoid factor (RF) &C-reactive protein (CRP)), haematological & biochemical changes (e.g. Creatine phosphokinase & lactate dehydrogenase, serum proteins,protein profile by gel electrophoresis & hormons) were performed in addition to the clinical picture. Rcsults;- According to the results of histological diagnosis the 72 patients were divided into six groups; Muscular dystrophy (12 patients), myopathy (45 patients), Neuromyopathy (3 patients), Neuropathy (4 patients), no significant pathological changes (4 patients), and non specific pathological changes (4 patients). The histopathological changes investigated included the presence of angulated fibers, round-dark stained fibers, fragmented, hypertrophic fibers, endomysial fibrosis, fatty tissue replacement, phagocytosis and necrotic fibers in comparison with other histopathological changes found without significant variation between groups of patients. In this study the histochemical enzymes reactions (Alpha-naphthyl acetate esterase and succinate dehydrogenase) illustrated good and poor fiber type differentiation. Significant number of patients with muscular dystrophy (10 (83.3%)) and 11 patients (24.5%) with myopathy presented with poor fiber typing. Ultrastructural study was performed for 8 cases using transmission electron microscope, and revealed a good correlation with light microcsope findings. EMG findings established the importance of this technique in a group of patients presented histologically with non specific pathological changes and in the group of patients with no significant pathological changes by demonstrating 3 patterns neuropathic, myopathic and normal pattern. Serum creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) were significantly increased, the mean level of CPK was elevated (mean 377.26 ±434.61 IU/L with range of 12-1910 IU/L, the median 165) incomparison to the control group (mean 125.38 ±49.72 IU/L with the range of 35-197 IU/L), while for LDH the mean was 168.49 ±71.78 IU/L with the range of61-423 IU/L, in comparison to the control group (mean 128.77 ±42.72 IU/L with the range of 68-310 IU/L). The highest results reported in patients with muscular dystrophy, myopathy, neuropathy & neuromyopathy respectively. Protein electrophoresis on polyacrylamide gel demonstrated different 7 protein patterns ranged between 8-14 bands in patient's sera and all the patients with Duchenne muscular dystrophy manifest 9 bands in their protein profile, while 23% of patients with inflammatory myopathy manifest 10 bands. The results also showed that all the patients sera included band number 1 (MW=707000 dalton) and band number 12 (MW=25000 dalton, may mostly represent transferrin which increased in hypochromatic anemia). The results showed a significant increase in total serum protein (mean 6.437 ±0.69 mg/dL with the range 4.8-7.7 mg/dL) in patients with muscular dystrophy predominantly in patients with Duchenne muscular dystrophy (mean 7.125 ±0.191 mg/dL with the range 6.9-7.5 mg/dL) and this may reflect the deterioration of patients health. Hormonal assesments (Triiodothyronine (T3) ,Thyroxin (T4)) were performed for five patients, showed significant increase in their levels (the mean 2.89 ng/ml with the range 14. 12 ug/dL with the range 9-1 8.9 ug/dL for T4). Haematological study reflects no significant increase in WBC count but there was significant difference in the differential count of monocyte & granulocyte percentage, while serological study (C-reactive protein and Rheumatoid factor) not significantly reflect the inflammatory response of the immune system. Antinuclear autoantibodies and antireticulin autoantibodies with high percentage in the patients whom presented with myopathy (9(20%)) in comparison to other groups of patients. In Conclusion:- All the previous diagnostic aspects emphasized their importance as coalescence means (work together) for reaching the final, correct & precise diagnosis. However the priority is given for enzymatic evaluation. histopathological and histochemical, EMG findings, haematologicaL immunoiouical & serolotiical investiaations