The authors studied the parathyroid glands from 100 previously healthy subjects who died suddenly and were admitted to the Dade County Medical Examiner's (ME) morgue and from 66 inpatients who died at Jackson Memorial Hospital (JMH). Parathyroid glands in patients with diseases (JMH series) were heavier than those in healthy persons (ME series), and both groups of glands were significantly heavier than those previously reported. Mean glandular weight in white subjects was 42.6 +/- 20.3 mg, with a range of 22-103 mg. The 95% upper limit of gland weight for healthy white subjects was 73.1 mg and for black subjects, 91.6 mg. The size and weight exhibited a skewed distribution. Gland weight varied with age, increasing to a maximum in the 41-60 year old age group in all subsets except white women, in whom it continued to increase till after age 70. There was slight correlation (r2 = 0.15) of gland weight with body weight within series and race groups; parenchymal content of the glands was not constant but correlated positively with glandular weight. Glands from both series had a comparable fat content. Fat was unevenly distributed throughout the gland, and its amount was highly variable, ranging between 0 and 90%, with a mean of 26% for white subjects and 24% for black subjects in both series. Therefore, percentage fat may not be used as an index of hyperplasia. Healthy back subjects had heavier glands than healthy white subjects, unaccounted for by differences in body weights; this difference was not statistically significant in subjects with disease. Within the black race, glands were not significantly heavier in disease than in health, and in the few cases with serum calcium determinations, the gland weight did not vary inversely with serum calcium levels as in white subjects, suggesting a basic difference in parathyroid calcium metabolism between the two races.