In the course of study on the microbial transformation of p-aminosalicylic acid derivatives, Black Aspergilli (Asp. awamori 5002 and Asp. aureus 5494) was found to produce metabolic products. These metabolites have been isolated, purified and identified as N-acetylated compounds by comparison with the synthetic compounds by thin-layer chromatography, infrared spectrophotometry and nuclear magnetic resonance spectroscopy.