We measured antitetanus toxoid antibody responses after blunt (n = 24) and penetrating (n = 7) trauma and compared them with responses in patients without trauma (n = 55). Patients were defined as anergic or reactive on the basis of delayed type hypersensitivity response. The response to tetanus toxoid vaccination on admission of patients surviving trauma for over 2 weeks was defined as the ratio of day 14 to day 0 serum IgG antitetanus toxoid levels. Antitetanus toxoid responses were normal after both blunt and penetrating trauma. When stratified according to delayed type hypersensitivity responses, patients with trauma showed better antibody responses than patients without trauma. Major infection rates were similar between trauma groups (three of 24 with blunt trauma vs two of seven with penetrating trauma) and independent of delayed type hypersensitivity (two of 20 reactive patients vs three of 11 anergic patients), in contrast to patients without trauma (one of 19 reactive patients vs 15 of 36 anergic patients). We conclude that decreased delayed type hypersensitivity after moderate trauma is temporary, and that this transient immunodeficiency is not as strongly associated with reduced antibody responses and increased risk of infection as anergy in surgical patients without trauma.