An in-use study was done to determine the effect of transportation delay on the microflora of clinical specimens collected for microbiological analysis in a 1,000-bed university hospital. Portions of wound, respiratory, and urine specimens were planted for bacterial isolation on the wards immediately after collection. The remainder of each specimen was kept at room temperature without or without holding medium until it was picked up by messengers and taken to the bacteriology laboratory. The results of immediate planting on the ward were compared with those obtained by planting in the laboratory. Alterations in microflora were observed in all three types of specimens after averages of 2 to 4 hours of delay in planting.