Intracardiac blood pressure was determined in twenty-seven healthy adult mongrel dogs weighting 14-32 kg. Cardiac catheterization was used to measure intracardiac blood pressure. A Pingtail catheter was placed in the aorta and the left ventricle via the A. carotis communis, and a Swanz-Ganz catheter was placed in the right ventricle via the V. jugularis. End-systolic blood pressure was found to be 113+/-3.1 mm/Hg in the left ventricle 53+/-2.9 mm/Hg in the right ventricle, 3+/-2.5 mm/Hg in the left atrium, 3+/-1.3 mm/Hg in the right atrium and 127+/-3 mm/Hg in the aorta. In addition, times of contraction, relaxation, filling, preejection and ejection of the heart were calculated using blood pressure traces. While there was a positive correlation between end sistolic blood pressure in the aorta and end sistolic blood pressure in the left ventricle (r=0.071, p<0.001), there was a negative corelation between RV relaxion time and Ao end sistolic blood pressure (r=-0.064, p<0.05).