The activity of monoamine oxidase (MAO) in cow serum undergoes considerable fluctuations in the course of the oestrous cycle. The aim of the study was to determine the activity of MAO and its isoenzymes A (MAO-A) and B (MAO-B) in cow serum near the parturition. The experiments were performed on 8 pregnant and clinically healthy cows of the Polish Black and White Breed. Peripheral blood samples were collected every 4 hours before, during and after parturition. MAO serum activity was determined with the use of the spectrofluorimetric technique according to Matsumoto et al. (1985) with own modifications. Analysis of serum samples showed that MAO activity increased rapidly near the delivery. MAO-B activity was significantly higher than MAO-A activity and determined the profile of total MAO (MAO-T) activity. It may be suggested that an increase in MAO activity observed near delivery protects against an excessive elevation of catecholamine concentration in blood. However, the control mechanism and physiological role of MAO during this period need further investigations.