In the present study, it was aimed to compare the serum progesterone (P4) and 17β-estradiol (E2) levels detected by radioimmunoassay (RIA) and electrochemiluminescence immunoassay (ECLIA) and to investigate the accuracy of ECLIA method to measure serum P4 and E2 levels in 25 bitches. This study was carried out on 25 bitches of differentbreeds weighing 10-30 kg, at various phases of sexual cycle. The vaginal cytology was used to determine the phases of oestrus cycles. The correlation between the levels of P₄ and E₂ detected by RIA and ECLIA was analyzed statistically.

The percentage of animals in anoestrus (n=15), prooestrus (n=4), estrous (n=4) or dioestrus (n=2) were 60%, 16%, 16% and 8%, respectively. In the present study, it was observed that the serum P₄ (P<0.001; r=0.998) and E₂ (P<0.001; r=0.998) levels detected by RIA and ECLIA were similar and statistically significant.

In conclusion, it is suggested that ECLIA is as reliable method as RIA method for measuring P₄ and E₂ in bitches, and ECLIA method is more practical than RIA due to its shorter testing time.