We studied 101 patients (88 men and 13 women, mean age 54.5 +/- 10 years) who arrived at the hospital during the first 6 hours of acute myocardial infarction evolution. Our objective was to assess the reliability of clinical and laboratory signs of recanalization using intravenous streptokinase as a thrombolytic agent. The mean time between the beginning of infusion and coronary arteriography was 53.83 +/- 43 hours. The positive predictive values for pain, arrhythmia, ST segment and enzymes were 97.9%, 94.2%, 91.8% and 90.8%, respectively; the negative predictive values were 46.8%, 40.8%, 37.2%, and 50% in the same order. Sensitivity was 65.7%, 62.8%, 58.4% and 77.6% and specificity 95.6%, 86.9%, 82.6% and 73.9%, respectively. The positive predictive value, calculated on the basis of the presence of each variable alone or in association showed a probability of recanalization of 76.9% for one sign, 84% for two, 96.3% for three and 100% for all four. When we compared the positive predictive values of each variable according to the interval between the beginning of pain and admission to the hospital (during the first 3 hours or between 3 and 6 hours) our results were 100%/94% for pain (P = NS), 97%/88% for arrhythmia (P = NS), 100%/75% for ST segment (P = 0.004), and 97%/80% for enzymes (P = 0.019). The same analysis applied to negative predictive values showing 22%/62% (P = 0.007), 17%/55% (P = 0.008), 21%/47% (P = NS), 27%/61% (P = NS) for pain, arrhythmia, ST segment and enzymes, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)