Abstract We investigated the effects of Dazmegrel, a highly effective and selective thromboxane synthetase inhibitor, on the immune system in a bilateral 5 per cent total body surface area (TBSA) deep partial thickness scald in a guinea-pig model. The animals were randomized into two groups: one received Dazmegrel at 3·4mgkg 1 day 1 by i.m. injection; the other received the same volume of saline. Cell-mediated immunity was evaluated by the response to the hapten dinitrofluorobenzene (DNFB), as measured by ear swelling in response to cutaneous application. The ear swelling of the Dazmegrel-treated group was 52·8±3·8 per cent, compared to 41·4±2·4 per cent for the control group ( P<0.02). Neutrophil bactericidal function was determined on post-burn day (PBD) 7 and opsonic function on both post-burns days 7 and 22. The serum opsonic indices were nearly identical at both times, but the Dazmegrel-treated animals had a significantly improved neutrophil bactericidal index (1·15±0·05v. 1·68±0·17, P<0·01). Dazmegrel exerted a stimulating effect on the immune system in this burn model, improving neutrophil antibacterial function and cell-mediated immunity.