BACKGROUND This study was performed to investigate the effect of temperature of blood cardioplegia on the recovery of postischemic cardiac function. METHODS Pigs on cardiopulmonary bypass were subjected to global ischemia (30 minutes), followed by cold (n = 10) or warm (n = 11) continuous antegrade blood cardioplegia (45 minutes) delivered at 55-60 mm Hg. RESULTS Global left ventricular function, evaluated by preload recruitable stroke work, decreased with cold cardioplegia from 91 (85-103) [mean (quartile interval)], at baseline, to 73 (55-87) erg x 10(3)/mL postbypass (p = 0.03), but was unchanged after warm cardioplegia; 110 (80-132) to 109 (71-175) erg x 10(3)/mL (p > 0.5). However, the difference between treatment effects was not significant (p = 0.25). Diastolic function, evaluated by end-diastolic pressure-volume relation, deteriorated without any difference between groups. Mean cardioplegic flow was similar between groups. Coronary vascular resistance increased at constant rate during warm cardioplegic delivery, but remained unchanged with cold cardioplegia (p = 0.001 between regression coefficients). CONCLUSIONS No significant difference was found in postischemic functional recovery comparing cold and warm continuous blood cardioplegia. Cold cardioplegia is therefore preferred due to added safety of hypothermia.