Chorioallantoic artery blood flow and heart rate were studied in the chick embryo from stage 34 until stage 43 (d 9-16 of 21-d incubation). Baseline blood flow profiles of the chorioallantoic artery were measured with a flow probe (Transonic) in 100 chick embryos. The eggs were opened at the air cell and placed in a small plexiglass box with a continuous gas flow of a N2/O2 mixture (5 L/min), at 38 degrees C and 60% humidity. The chorioallantoic artery was localized near the fetal abdomen and placed in the lumen of the Transonic flow probe. The heart rate was derived from the blood flow signal. The mean chorioallantoic artery blood flow rose from 0.35 +/- 0.14 mL/min (mean +/- SD) at stage 34 to 3.13 +/- 1.49 mL/min at stage 43 (R2 = 0.69, p < 0.0001), which correlated with an increase in body weight (1.51 +/- 0.18 g to 15.08 +/- 0.76 g). Heart rate increased from 195 +/- 38 beats/min at stage 34 to 289 +/- 13 beats/min at stage 43 (R2 = 0.38, p < 0.0001). The chorioallantoic artery blood flow, which in avian species correlates with umbilical blood flow in mammals, increased with incubation time as reported in the mammalian fetus. This study shows that the chick embryo could be useful as a preparation for further perinatal cardiovascular research.