Owing to the limited availability of donor hearts, standard donor criteria for heart size matching need to be reexamined. The current practice at most centers is to match the donor's body weight to within +/- 20% of the recipient's. Our hypothesis was that minimal differences exist in heart sizes of the adult donor population, and therefore, the donor pool could be expanded for any given patient. M-mode echocardiographic measurements of left and right ventricular internal dimensions, left ventricular mass, and percent fractional shortening were reviewed in 235 normal adult subjects (101 men, 134 women). Low correlation coefficients and a high degree of variance were consistently observed between cardiac parameters and body size. There were no significant differences in left ventricular internal dimension when women weighing 40 to 109 kg were compared with men statistically different among men weighing 50 to 99 kg. No difference was noted in right ventricular size among men and women. Echocardiography is a simple and accurate technique to assess cardiac dimensions. Body weight does not correlate well with adult cardiac size and should not be used as an exclusion criterion for a donor heart.