High (8%) and low (0.3%) NaCl diets were administered for 3 weeks before testing inbred Dahl salt-sensitive (SS/Jr) or salt-resistant rats (SR/Jr) for altered susceptibility to cerebral infarction after occlusion of the middle cerebral artery. At occlusion time, mean systolk blood pressure (BP) was 201 ± 7 mm Hg in SS/Jr fed a high NaCl diet. Two weeks later an atrophied infarct was present in the territory of the occluded artery of all (n= 10) hypertensive SS/Jr, and infarct size was correlated with BP at occlusion time (p< 0.01). In normotensive control SS/Jr fed a low NaCl diet (n= 11), BP (118 ± 3 mm Hg), frequency of infarction (18%), and infarct size were all significantly less (p< 0.05) than in the hypertensive rats. In SR/Jr fed a high (n= 11) or low (n= 10) NaCl diet, BP was not statistically different (112 ± 4 vs 116 ± 4 mm Hg). Cerebral infarction frequency was significantly (p< 0.05) greater in SR/Jr fed a high NaCl diet (73%) than in SR/Jr receiving a low NaCl diet (20%), but infarct size was not correlated with BP hi SR/Jr (Pgt; 0.05). Thus, elevated NaCl intake in SS/Jr and SR/Jr before middle cerebral artery occlusion predisposes to cerebral infarction, but differences in infarct size and its correlation with BP suggest the controlling factors are not identical in the two strains.