The altered contractility that occurs in cardiac hypertrophy and heart failure (HF) is often attributed to changes in Ca2+ handling properties (Hasenfuss and Pieske, 2002). Such changes have been less extensively studied in the right ventricle (RV), compared to the left ventricle (LV), thus the aim of this study was to investigate alterations in Ca2+ handling in RV hypertrophy and HF in pulmonary hypertensive rats. Male Wistar rats (200 g) were injected with monocrotaline at 30 mg/kg to induce RV hypertrophy (HYP) or 60 mg/kg to induce RV failure (FAIL) which was identified by clinical signs. Control animals were injected with an equivalent volume of saline (CON). Animals were humanely killed 3-4 weeks after injection and RV cardiomyocytes were enzymatically isolated. All experiments were conducted at 20-24°C. Cell shortening and Ca2+ transients were recorded in fura-4 AM loaded myocytes. Caffeine (20 mM) was used to assess the sarcoplasmic reticulum (SR) calcium load. Calcium sparks were measured by confocal microscopy using the fluorescent indicator fluo-4 AM. Statistical comparison between CON, HYP and FAIL myocytes was performed by 1-way ANOVA. All procedures accorded with current UK legislation. Compared to CON hearts; there was a statistically significant increase in the ratio of heart weight: body weight by 50% in HYP and by 78% in FAIL heart (P < 0.05, n = 5-6 hearts in each group). Cell shortening was significantly decreased by 17% in HYP and by 29% in FAIL myocytes but Ca2+ transient amplitude significantly increased by 43% in HYP and 56% in FAIL myocytes, (P < 0.05 n = 17-20 myocytes in each group). SR load was also increased in HYP by 20% and FAIL by 61% myocytes (P < 0.05, n = 19-23 myocytes in each group). Consistent with an increase in SR load, the frequency, duration and width of calcium sparks significantly increased in the development of hypertrophy and HF but spark amplitude progressively reduced (P< 0.05, n= 24-32 myocytes in each group). Ca2+-handling is altered in the RV hypertrophy and heart failure associated with monocrotaline-induced pulmonary hypertension. The increased SR load may explain the observed increase in Ca2+ transient amplitude and the increased number of Ca2+ sparks. However, these changes cannot be directly responsible for the reduced cell shortening, this is probably related to de-sensitization of the myofilaments to Ca2+ (Lamberts et al., 2007).