This paper is concerned with the effects of Lorcainide (LCN) and Amiodarone (AMD) on stress-induced myocardial lesions in rats. Forty rats were used. The first group (G-1) was used as a control (n = 10) and animals were injected with saline. Animals in group 2 (G-2) (n = 15) received AMD 10 mg per kilogram, and animals in group 3 (G-3) (n = 15) received LCN 3 mg per kilogram. During five minutes before the injections, the rats were submitted to a stress, consisting of intermittent cold water jets (6 degrees C). Animals were sacrificed one hour after injection, and the hearts were histologically studied. The relative areas of necrotic myocardium were assessed by Bertazzoli's modified method. In G-1, myocytolysis in the subendocardium of left ventricle (score: 2.2 +/- 0.79), contraction bands (1.2 +/- 1.03) and subendocardial myocardial damage (0.8) were common findings. In groups G-2 and G-3, the lesions described were found, but to a lesser degree; subendocardial myocytolysis: 1.6 +/- 0.63 and 1.07 +/- 0.4; contraction bands: 0.67 +/- 0.82 and 0.07 +/- 0.26; and subendocardial damage: 0.77 and 0.40. LCN and AMD markedly decreased stress-induced myocytolysis (p less than 0.01) (graph 1), but LCN was more effective than AMD (p less than 0.05). Comparison of severity and extension of contraction bands showed that only LCN had a significant effect (p less than 0.01) (graph 2); the same was observed as regards the decrease of damaged zones (p less than 0.05). From our data, LCN and AMD appears to have the capacity of reversing some of the stress-induced myocardial damage in rats.