A procedure has been developed for rapid mineralization of milk and dairy product samples with different reagents in closed vessels in a microwave oven, which is compatible with a final spectrophotometric determination of phosphorus that is performed following standardized procedures. Perchloric acid along with hydrogen peroxide gave the best digestion performance without interference in the subsequent spectrophotometric measurement. The sample exposure time in the microwave oven was 15 min. The results for the various product assays were compared with the results of incineration of identical samples in a crucible furnace. The two procedures gave similar levels of precision, with coefficients of variation of around 2%. Accuracy was evaluated using certified milk samples and the values obtained were within the confidence intervals for these products. The authors wish to acknowledge financial sup- port for this research project (ALI93-0005-CP) from the Comision Interministerial de Ciencia y Tecnologia.