Serum zinc levels were assayed in patients with AIDS and related syndromes, using spectrophotometry and atomic absorption. Statistical data have shown that serum zinc levels, in addition to being significantly lower (p less than 0.001) among different groups and controls, decrease progressively with the worsening of the clinical and immunological picture from LAS to AIDS. Serum zinc levels in patients with AIDS and ARC have, moreover, been demonstrated to be related (r = 0.8240; p less than 0.001) to the lymphocyte subset CD4 helper-induced. These results suggest that serum zinc determination and possibly zinc therapy might be reasonably considered in the management of patients with symptoms of HIV infection.