Evidence is presented that human neutrophils contain catecholamines and several of their metabolites. In vitro, incubation with alpha-methyl-p-tyrosine or pargyline affects intracellular dopamine, norepinephrine and their metabolites, suggesting catecholamine synthesis and degradation by these cells. Reserpine reduces intracellular dopamine and norepinephrine and desipramine reduces intracellular norepinephrine, suggesting the presence of storage and uptake mechanism. In view of the ability of catecholamines to affect neutrophil function, the present results support the hypothesis that autoregulatory adrenergic mechanisms may exist in these cells.