"There are potential environmental concerns from the disposal of municipal wastewater effluents and sewage treatment plant sludges. This report summarizes the microbial mutagenic evaluation and chemical analysis of 13 sewage sludge samples from various sewage treatment plants located in Texas and Washington state. The sewage sludge samples were air-dried followed by sequential Soxhlet extraction with three organic solvents of increasing polarity, i.e., pentane, methylene chloride, and methanol. The organic extracts from three of the samples were further fractionated by normal phase high- pressure liquid chromatography (HPLC). The obtained extracts and fractions were bioassayed for microbial mutagenic response using the standard histidine reversion assay with Salmonella typhlmurium strains TA98 and TA100, both with and without S9 metabolic activation. Extracts and fractions were chemically analyzed by high resolution gas chromatography (GC) using a variety of element-specific detectors, gas chromatography/mass spectrometry (GC/MS), and (to a lesser extent) liquid chromatography/mass spectrometry (LC/MS). "--P. .