Nocardia asteroides and N. brasiliensis strains were found to possess acid phosphatase activity. This enzyme was found to be cell-associated and its activity paralleled the cell mass increase seen during the Nocardia growth cycle. Of the strains tested, N. brasiliensis exhibited the highest enzymatic activity. Implications of these findings are related to current evidence which indicates that other microbial acid phosphatases may constitute potential pathogenic factors for humans.