A novel indicator plate method was developed for screening of aliphatic-nitrile-degrading bacteria. Isolated bacteria were tested for utilization of acetonitrile as sole source of carbon and nitrogen with the release of ammonia. The released ammonia causes increase of the pH of the medium. Phenol red indicator is used for detection of ammonia based on colour change of the indicator dye from red to pink. The liberation of ammonia from aliphatic-nitrile-utilizing bacteria is also studied in plates containing other indicators such as bromothymol blue and phenolphthalein. The usefulness of the indicator plate is demonstrated for bacteria that degrade certain aliphatic nitriles. Bacteria degrading nitriles as a nitrogen source can also be isolated with a medium containing additional carbon source. This plate method would be useful in isolation and screening of bacteria for degradation of aliphatic nitriles and also for production of nitrile-hydrolyzing enzymes.