With the advent of techniques to isolate large numbers of single adult mammalian ventricular myocytes, it has become possible to determine whether, as a result of the different pressure loading of the right and left ventricles (RV and LV), RV and LV myocytes differ in electromechanical properties. We studied the morphology, contraction and electrophysiology of the L-type slow inward calcium current (Isi) in isolated adult feline RV and LV myocytes. The maximum width of LV myocytes was slightly greater than for RV myocytes (25.9 +/- 7.0 microns vs. 25.1 +/- 7.9 microns, P = 0.05), but RV and LV myocytes did not differ significantly in maximum length or two-dimensional surface area. RV and LV myocytes did not differ significantly in the extent of shortening or rates of shortening and relaxation. The voltage dependence of activation and inactivation and the time course of activation and recovery from inactivation of Isi also did not differ significantly between RV and LV myocytes. We conclude that despite the different pressure loads on the RV and LV, single myocytes from either ventricle have similar physiologic properties.