One hundred and three subjects with ischemic heart disease (IHD) were followed-up in an attempt to assess the most important factors affecting morbidity and mortality. At the time of initial examination 23 patients had congestive heart failure. During the one year follow-up after the examination 11 patients died. Various parameters including perfusion defects (SCORE) on ²⁰¹Tl-myocardial scintigrams, radiocardiographic hemodynamic data and orthogonal electrocardiographic parameters were analysed at the onset of the study, according to the method of "factor analysis". The factor analytic technique enabled a summary of the data obtained from these non-invasive approaches into five major interpretable components termed factors 1 to 5 ; factor 1 as "the extent of myocardial ischemia", factor 2 "heart size", factor 3 "cardiac pump function", factor 4 "peripheral blood volume" and factor 5 "QRS forces". The relationship between these five factors with a one-year mortality rate was then investigated. Of these factors, factor 1 which included SCORE, spatial G/QRS, T/QRS and QRS-T angle proved to be the most important as related to morbidity and mortality in IHD. Factors 2 and 3 were also shown to be useful prognostic indicators of subsequent mortality. Thus, a combination of these non-invasive parameters is useful not only to diagnose IHD but also serves as one form of evaluation of the prognosis in patients with IHD.