Abstract: Steganography is the art of information hiding in ways that prevent its detection. A message in cipher text may raise suspision, while an invisible message will not. Digital steganography uses a host data or message, known as a ''container'' or ''cover'' to hide another data or message called ''secret'' in it. An Image in audio steganography system had been proposed in this thesis in order to embed a secret image data in audio data. One embedding method is implemented in the proposed system (Least Significant Bit in time domain, and transform domain Discrete Wavelet Transform). The technique (Least Significant Bit) is implemented in time domain where the secret data is embedded directly in the cover data. This technique is implemented in frequency domain that results from using discrete wavelet transform; where the secret data are embedded in wavelet transform (WT) coefficients of cover data. Most of the fidelity measures (Mean Square Error, Normalized Root Mean Square Error, Signal to Noise Ratio, Peak Signal to Noise Ratio and Correlation) obtained in the test has indicated good results for PSNR (187.28db) and MSE (0.214). The reconstructed data is exactly the same original data if the wavelet transform is used, while a small unrecognizable error may occur when the technique is used in time domain. MATLAB programming environment is used to simulate the entire system.