The aim of this study was to compare progesterone concentrations in bitches during ovulation with a different course of follicular collapse as determined by ultrasonography. The study was conducted on 36 animals of different breeds, from 2 to 7 years old, and from 2 to 44 kg of body weight. Ultrasound examinations of ovaries were conducted in the peri-ovulatory period until ovulation was detected. Based on USG scans the animals were divided into two groups: group A with fast follicular collapse within 1 day, and group B with gradual follicular collapse within 2-3 days. Progesterone measurements were performed in both groups on the day when the beginning of ovulation was diagnosed by USG. Follicular collapse in group A was observed in 27.8% of animals (n = 10) and in group B in 72.2% (n = 26). There were no statistical differences (p < 0.05) in progesterone concentrations between groups A and B (6.68 +/- 0.92 ng/ml and 6.81 +/- 0.57 ng/ml respectively). From 31 bred bitches (natural mating or insemination) pregnancy was confirmed in 29 females (93.5%). These results provide information about the sufficient stability of progesterone concentration during ovulation regardless of the follicular collapse speed. Ultrasonography during the peri-ovulatory period combined with progesterone measurements allows progress in ovulation management.