The procedure is described for parallel determination of two aflatoxin preeursors-sterigmatocystin (STC) and O-methylsterigmatocystin (OMSTC) in milk. The mycotoxins were extracted with chloroform from skimmed milk. The extract was purified with gel permeation chromatography and extract components were separated using two dimensional thin-layer chromatography on silica gel. Fluorescent densitometry was used for the quantitative measurement of toxin levels. The detection limit of the method was 1 /µg/kg and the average recoveries were 81 ±2% and 67±4% for STC and OMSTC respectively, at the contamination levels of 3 /µg/kg, 2 µg/kg and 1 µg/kg.