Technetium pyrophosphate myocardial scintigraphy has become, together with Thallium scintigraphy, a common diagnostic aid in recent myocardial infarction. However, some cases with moderate diffuse fixation (2+ diffuse in Parkey's classification) are considered equivocal results by many workers. We tried to assess the value of emission tomoscintigraphy in classifying these border-line cases. This non-invasive investigation requires sophisticated equipment, including a rotating gamma camera coupled to a computer. The computer reconstructs tomographic images in the three planes (frontal, sagittal, transverse) at 6 mm intervals. After analysis of 34 coronary patients using classical clinical criteria, standard and tomographic scintigraphy were performed and the results interpreted by a double blind procedure. The following conclusions were drawn: Interpretation of the results of tomography was more reproducible than that of standard scintigraphy (91 p. 100 compared with 79 p. 100). The sensitivity of detection of myocardial infarction was higher (96 p. 100 compared to 80 p. 100) without any loss of specificity (preliminary study in 15 non-coronary patients); this improvement is due to the elimination of the "equivocal" cases observed on standard scintigraphy. The infarcted area was easier to determine as the interpretation was more reproducible. The estimation of the size of the infarcted area and the detection of rudimentary infarcts did not seem to be improved by emission tomography. Our criteria of positivity for the tomographic images were : at least 2+ fixation (significant but less intense than that of the sternum); fixation visible in at least 2 different tomographic planes (e.g. sagittal and frontal); fixation visible on at least 2 consecutive images in each plane.