Air contamination was measured in a down-flow, clean air enclosure during 50 total hip arthroplasties to compare the effect of different scrub suits and operating gowns. In one series, with cotton clothes, the operating gowns used were either disposable nonwoven operating gowns or total body exhaust gowns. With the exhaust gowns the median air contamination, measured as colony-forming units (cfu)/m3, was reduced by about 5 times, to 0.3. In another series, nonwoven operating gowns were used together with scrub suits made of either cotton or one of two types of synthetic materials. The latter two scrub suits were equipped with elastic sealings at the openings. With both of these types the median air contamination, compared to cotton scrub suits, was reduced by about one half, to 0.4 cfu/m3. The authors conclude that both specially designed scrub suits and exhaust gowns can further reduce an already low level of bacterial air contamination in a down-flow, clean air enclosure.