Abstract: Ultrasonographic examinations of 10 pregnant bitches with known breeding dates were made on successive days to establish the identifiable characteristics of pregnancy. Subsequent serial examinations were made to sonographically characterize normal canine prenatal development based about the first mating. The initial detection of the fetal and extra-fetal structures were as follows: gestational sac at day 17.88 ±1.13 (16-21); zonary placenta in the uterine wall at day 23.70 ±0.78 (23-25); embryo initial detection at day 22.80 ±1.03 (21-24); heartbeat at day 23.0 ±0.94 (22-24); yolk sac membrane at day 24.8 ±0.78 (24-26); amnionic membrane at day 26.81 ±0.60 (26-28); fetal movement at day 30.40 ±1.64 (28-32); stomach at day 33.40 ±1.07 (32-35); urinary bladder at day 34.90 ±1.19 (33-37); skeleton at day 35.10 ±0.73 (34-36).