The effects of the CultureSwab (Difco Laboratories, Detroit, Mich.) and Culturette II (Marion Scientific, Div. Marion Laboratories, Inc., Kansas City, Mo.) transport systems on the viability of 95 clinically significant bacteria were studied. Organisms included staphylococci (8 isolates), streptococci (22 isolates), Haemophilus spp. (16 isolates), members of the family Neisseriaceae (14 isolates), Bordetella spp. (5 isolates), members of the family Enterobacteriaceae (16 isolates) and pseudomonads (14 isolates). Viability counts with both methods usually dropped by greater than or equal to 90% after incubation at room temperature for periods ranging from 4 to 48 h, and statistically significant differences between the two methods were not observed. However, counts were generally higher with the Difco method, and this difference may be clinically important.