The aim of this study was to determine possible links between steroidogenic activity of single ovarian cysts and response to intramuscular treatment with 20 microg of buserelin (GnRH-analogue) after cyst emptying, in pluriparous Friesian cows bearing a singleton cyst treated not earlier than 55 days post-partum. Progesterone, 17beta-estradiol and testosterone were determined in cystic fluids collected by needle aspiration of the cyst. Of the cows, 75.6% began ovarian cyclicity within 30 days after treatment with a conception rate of 64.7%. In this study it was found that as progesterone concentration in cystic fluids rose, the number of positive responses to the treatment fell.