85 vectorcardiograms, characterized by anteriorly oriented horizontal ventricular loop, were analized in order to evaluate if this pattern can be considered diagnostic at all for strictly posterior myocardial infarction. Records were divided into two groups according to positivity or negativity of clinical history for myocardial infarction. Records consistent with right ventricular hypertrophy were ruled out. Nine parameters related to ventricular depolarization and repolarization were measured and the values were submitted to statistical analysis. The study showed that:--selection of the two groups was correct, because of first group's homogeneity and control group's unhomogeneity;--mean values of the nine parameters did not differ significantly in the two groups;--single parameter into each group was unrelated to others. As a consequence, criteria at the time in use for diagnosis of strictly posterior myocardial infarction seem not to be useful, as other conditions beside myocardial infarction or right ventricular hypertrophy are able to determine the same vectorcardiographic pattern.