An evaluation of the effect of total body exhaust clothing on air and wound contamination was made in an operating theatre with a zonal ventilation system. Sixty-four patients who underwent total hip replacement using the Charnley-Müller prosthesis were studied. The members of the surgical team wore total body exhaust suits (TBE-suit), or conventional theatre clothing (C-clothing) at alternate operations. Nearly half of the patients in each group were given prophylactic antibiotics. Both the mean and median values of airborne bacteria in the operating theatre were significantly lower during operations with TBE-suits than with conventional theatre clothing. The lowest number, 4.0 cfu/m3, was found at the site of the operation wound. Cultures from adhesive drapes showed growth in 46 per cent of the C-group and in 43 per cent of the TBE-group samples. Wound washouts showed growth in 43 per cent of the C-group and in 10 per cent of the TBE-group samples. Staphylococcus epidermidis was the most frequently isolated bacteria both from adhesive drapes and from wound washouts. The rate of superficial infections was slightly higher when C-clothing was used. Deep infections were found in one patient in the TBE-group and in two patients in the C-group. None of the infected patients had received prophylactic antibiotics.