37 patients with mixed cardiac pathologies were subjected to isometric exercise (hand grip) during routine cardiac catheterization. On the basis of a simple and safe grip test it was possible to distinguish three groups of patients according to the left ventricular pressure at rest and its response to this test. Group 1 consisted of 14 patients with left ventricular end diastolic pressures remaining below 12 mm Hg both at rest and on exercise. These patients were considered to have normal left ventricular function some, even in the presence of organic heart disease. No deaths occurred in this group during the follow-up period which averaged 33.8 months. At the other extreme (Group 3) there were 12 obviously disabled patients with resting left ventricular filling pressures above 12 mm Hg rising further under isometric stress. Six of these patients (50%) died during the period of the study. (Average follow-up 21.4 months). By the application of the hand grip test, an intermediate population (Group 2) of 11 patients was discernible. These patients were able to maintain a normal cardiac reserve at rest (LVEDP less than 12 mm Hg) but not during isometric effort (LVEDP greater than 12 mm Hg). Two of these patients (18%) died during the follow up period (average 22.1 months). Assuming a pathological progression with time from groups 1-3 and in view of the different prognoses observed in the course of the long-term follow-up it would appear that the Group 2 patients should be considered more critically and offered more active management.