Clinical data from 186 patients (133 males and 53 females) with 190 episodes of infective endocarditis (IE) occurring between January 1981 and July 1991 were studied retrospectively at a large referral hospital in Northern India with the intention of highlighting certain essential differences from those reported in the West. The mean age was much lower (25 +/- SD 12 years, range 2 to 75 years). Rheumatic heart disease was the most frequent underlying heart lesion accounting for 79 patients (42%). This was followed by congenital heart disease in 62 (33%) and normal valve endocarditis in 17 (9%). Twenty-four patients had either aortic regurgitation (n = 15) or mitral regurgitation (n = 9) of uncertain etiology. Prosthetic valve infection and mitral valve prolapse were present in only 2 patients each. A definite predisposing factor could be identified in only 28 patients (15%). Postabortal sepsis and sepsis related to childbirth accounted for 6 and 5 cases, respectively. Only 1 patient had history of intravenous drug abuse. Two-dimensional echocardiography showed vegetations in 121 patients (64%). Blood cultures were positive in only 87 (47%), with a total of 90 microbial isolates. Commonest infecting organisms were staphylococci (37 cases) and streptococci (34 cases). Except for a significantly higher number of patients with neurologic complications in the culture-negative group, there were no differences between patients with culture-positive and culture-negative IE. Of the 190 episodes of IE, the patients had received antibiotics before admission in 110 (58%) instances. A significantly greater number of culture-negative patients had received antibiotics than did culture-positive patients (87 vs 23, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)