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Objective:To investigate some blood biochemical parameters in anoestrous dairy cows with cystic ovarian follicles(COF) during the first two months post partum and the effect of hCG-PGF2α-GnRH treatment on their reproductive response.Methods:The investigation was performed on20 lactatingHolstein cows, divided into two groups: control group(n=8) and treated group (n=12).All animals had cystic ovarian follicles, detected during the two consecutive transrectal ultrasound examinations at7-day interval.Blood samples from each animal were collected on the day of second ultrasonography(Day0) and subjected to a hormonal and biochemical analysis. Treated cows were subjected to another ultrasound examination on day of prostaglandin injection and the presence of corpus luteum was recorded.The control animals were not treated, while the treated group received1500IU hCG on day0,PGF2α500 mg on day7 and100 μgGnRH 48 hours latter.Eighteen hours afterGnRH administration animals bearing corpus luteum on Day7 were artificiallly inseminated.The last ultrasound examination was made forty days after start of the threapy.On the base of the obtained results, cumulative oestrous activity, cumulative ovulation rate, pregnancy rate andCOF persistence were determined.Results:The blood analysis in the both groups onDay0 showed significantly(P<0.05) lower mean concentration of progesterone, glucose and inorganic phosphate compared to the reference range values for cyclic dairy cows.Cumulative oestrous activity(91.7%) and cumulative ovulation rate(75.0%) were considerably higher(P<0.05) in treated group than control group, whereas the cystic follicle persistence(25.0%) was lower(P<0.05) in the treated group than control group.Conclusions:The present study confirmed the thesis for low blood levels of glucose and inorganic phosphate in cows presenting cystic ovarian follicles.It also indicated significant improvement of cumulative oestrous activity and ovulation rate in animals subjected tohCG-PGF2α-GnRH administration than non-treated animals.The used hormonal protocol could decrease cystic ovarian follicle persistence in dairy cows.