Changes in the spatial relationship between the sarcolemma and intracellular compartments may be an underlying reason for defective excitation-contraction coupling observed in heart failure (Gomez et.al., 1997). These changes may arise from a modified ventricular myocyte surface area: volume ratio (SA:V). The quantification of electrophysiological data are reliant on SA:V. However, this normalization factor is unknown in normal and hypertrophied murine ventricular myocytes and could be of relevance to studies on transgenic mouse models of hypertrophy. In this work, we calculated SA:V in the same myocytes isolated from normal and hypertrophied mouse hearts. Hypertrophy was induced by infusion of angiotensin II for 14 days (Ang II; 2 µg/min/kg) via an osmotic minipump implanted subcutaneously under isoflurane anaesthesia (inhalation 0.5-3.0%). Control mice received saline solution (Veh). Cardiac myocytes were isolated following cervical dislocation and voltage clamped to assess the membrane capacitance, an index of cell surface area (Terracciano et.al., 1998). The same cells were visualised with the fluorescent dye, di-8-ANEPPS, and optically sectioned by confocal microscopy. Cell volume was calculated by 3-D reconstruction of the images. Differences between means were assessed with a one-way ANOVA and Bonferroni post-test. A two-tailed Pearson correlation was used to assess differences between cell membrane capacitance and volume in Veh and Ang II groups.Following angiotensin II infusion, mice showed a significant increase in heart-weight-to-body-weight ratio indicating cardiac hypertrophy (Veh: 7.1±0.4 mg/g (5); Ang II: 9.4±0.7 mg/g (6), p<0.05); (means±S.E.M. (n)). Ventricular myocyte volume was significantly greater in Ang II, (34.4±1.4 pl (41)) compared with Veh, (27.1±1.5 pl (35, p<0.001)). Capacitance was also larger in Ang II, (237±7 pF (41)) compared with Veh, (177±9 pF (35, p<0.001)). The surface area: volume ratio was unchanged by hypertrophy: (Ang II: 7.33±0.40 pF/pl (41); Veh: 7.09±0.48 pF/pl (35, p=ns)).We conclude that, following the induction of hypertrophy in the murine heart, the ratio between cell surface area and cell volume is unchanged.