Plasma testosterone (T) was measured at 8-9 a.m. in 44 men chronically institutionalized in a Veterans Administration Nursing Home, and correlated with an extensive clinical data base (including age, diagnoses, drugs, laboratory tests, anthropometric measurements, and mortality during the year after the T analysis). Age averaged 76.4 years (range 60-95). Plasma T was below the lower limit of the normal range for healthy young men (i.e. less than 300 ng/dl) in 46% of the men studied. Samples containing low T (less than 300 ng/dl) also contained subnormal unbound T, but normal concentrations of thyroxine and cortisol. Of the low T samples, 45% contained elevated LH, FSH or both (over 20 mU/ml), and the remaining 55% contained LH and FSH levels below this threshold, these two subgroups representing peripheral and central hypogonadism respectively. Plasma T was significantly (p less than 0.02) correlated in a direct relationship with hemoglobin, serum cholesterol, and the occurrence of seizures.