Myocardial catecholamine levels have not yet been determined in the transplanted human heart. We measured norepinephrine, epinephrine, and dopamine in endomyocardial biopsies from 19 short-term (organ age, 6.6 +/- 6 months) and five long-term (organ age, 62 +/- 2 months) heart transplant patients. Results were compared with those from 10 normal control subjects. In 17 of 19 short-term heart transplant patients, myocardial catecholamines were undetectable, indicating values below 0.1 pg/micrograms noncollagen protein, which was the detection threshold of our assay. In the remaining two patients, myocardial catecholamines (pg/microgram noncollagen protein) were norepinephrine (1.4 and 3.2), epinephrine (0.8 and 1.9), and dopamine (0.9 and 2.3), respectively. In the five long-term heart transplant patients, myocardial catecholamines were not detected. Catecholamine concentrations in 10 healthy control subjects were norepinephrine (10.3 +/- 2.9), epinephrine (0.36 +/- 0.51), and dopamine (0.52 +/- 0.40). Low myocardial norepinephrine levels (less than 20% of control values) with unexplained high levels of epinephrine and dopamine were found in single transplant patients. In most heart transplant patients, however, myocardial catecholamines were undetectable up to five years after transplantation, indicating that the adrenergic response of these hearts probably depends on variations in plasma catecholamines or cardiac beta-receptor density.