Ultraviolet resistance in the extremely halotolerant bacterium Micrococcus sp. strain Gl was investigated. UV survival curves of strain Gl, Escherichia coli & Stapkylococcus aureus showed that strain Gl was much more resistant to UV radiation than E. coli & Staph. aureus. D37 values for strain Gl, E. coli & Staph. aureus were 22, 5 & 2 J/m respectively. Ultraviolet survival curves were also determined for strains Gl, GMA (lacking two plasmids) & GME (lacking three plasmids). It was found that strain Gl was more resistant to UV radiation than GMA & GME. D37 values for strains Gl, GMA & GME were 22,14 & 11 J/m2 respectively. It can be concluded that plasmids and/or pigmentation might have a role in ultraviolet light resistance, since both cured strains showed changes in their pigmentation. Nature of genes encoded for DNA repair systems (photoreactivation, excision & recombination) that are found in strain Gl was investigated. Results showed that the wild type (strain Gl), & the two cured strains (GMA & GME) possesses these three DNA repair systems. According to these results, it was concluded that the genes encoded for DNA repair systems are located within the genome. The effect of several factors on UV resistance of strain Gl were studied. Strain Gl cells grown in different concentrations of NaCl & MgSO.THzO were irradiated with UV light. Survival curves of strain Gl grown in 2, 10 & 20 % NaCl showed slightly difference in shoulder after UV irradiation for 10 J/m2. While strain Gl grown in 1 & 2 % MgSO4.7H2O showed higher shoulder than strain Gl in the absence (0%) of MgSO4.7H2O & there Dn values were 22, 21 & 11 J/m2 respectively. Results indicated that MgSOJHbO might play a role in protection against