The syndrome of peri-partum cardiac failure (PPCF) has been studied in 224 women seen in three years in Zaria, in northern Nigeria. A very high proportion were rural Hausa patients. There was a seasonal peak in July, and the incidence was about one per cent of deliveries. The risk increased with both age and parity. Symptoms began most commonly in the second week after delivery, and admission was commonest in the fourth. Typical signs of cardiac failure were found, and pulsus alternans, atrio-ventricular valvular incompetence, transient systemic hypertension and splenomegaly were common. The chest radiograph showed marked cardiomegaly, and extrasystoles and inverted T waves were often present in the electrocardiogram (ECG). Hypoalbuminaemia was common. Digoxin and diuretics were rapidly effective, causing a mean weight loss of 29 per cent in 15 days, resolution of hypertension, and a fall in the cardio-thoracic ratio (CTR) from 61 to 53 per cent. During the first year after diagnosis, the CTR became normal in 82 per cent of patients, and the ECG in 60 per cent. PPCF recurred, again with the same seasonal variation, after 19 per cent of subsequent pregnancies. During follow up for two to five years, 22 per cent of the women became hypertensive, and 11 per cent died. The prognosis was worst in those with an arrhythmia, hypertension, sustained cardiomegaly or aged 30 or more. Asymtomatic post-partum hypertension (PPHT) was found in 61 per cent of normal Hausa women, with a seasonal peak in May, especially in those with hypertension during pregnancy or labour, and twin pregnancies. Peri-partum cardiac failure may be due to the combined pressure load of PPHT, the volume load from eating the customary sodium-rich kanwa, and the cardiovascular demands of heat, both climatic and traditionally self-imposed.