Biodegradation of fats and oils in wastewaters has a potential role in wastewater management and water pollution control. Several enzymes and microorganisms are being exploited to carry out these processes. In the course of our work to design a system for treating wastewater with high concentrations of fats and oils, we developed an inoculum with high fat- and oil-degrading activities. The inoculum (designated as the JAT inoculum) was a mixed-culture of 15 bacterial isolates from various fatty wastewater samples, all isolates with a well-demonstrated ability to degrade fats and oils. Many of them could also quickly liquefy 12% gelatin and some could hydrolyse starch. The inoculum was effective in wastewaters with pH ranging from 4.5 to 9.5, but an optimum initial wastewater pH was in the alkaline range. The observed optimum treatment temperature when using the inoculum was 20-25 degrees C, but activities occurred within the range of 8 to 42 degrees C. Characteristics of the isolates suggested that there were no pathogenic species present. Biodegradative tests with the inoculum on samples of eight different fats and oils showed that several fats and oils could be degraded by the organisms in the culture. The inoculum is potentially useful for treating wastewaters containing fats and oils from both plant and animal origins.