The acid phosphatase in ungerminated conidia from Colletotrichum graminicola, a corn pathogen, was investigated using spectrophotometric and cytochemical methods. Acid phosphatase activity was studied in a homogenate obtained by fragmentation of ungerminated conidia. With p-nitrophenylphosphate as substrate, the apparent V_max and K_M were 1,000 nmol p-nitrophenol/mg of protein/min and 0.631 mM, respectively. The pH and temperature optima were 5.5 and 60oC, respectively. A cytochemical ultrastructural assay showed deposition of the reaction product inside vacuoles but not extracellularly on the cell surface. The permeabilization of conidia with Triton X-100 increased acid phosphatase activity eight fold. Compared to other procedures, our method was fast, easy to perform and gave consistent results.