Mammalian serum or bovine serum albumin are essential for Trichomonas vaginalis cultivated under axenic conditions. Unfortunately, these components inhibit several biological properties of these parasites. PACSR is a serum replacement, free of bovine serum albumin. used for axenic cultivation of Entamoeba histolytica. We show that PACSR is also useful for axenic cultivation of T. vaginalis. Tubes containing 5.5 ml PEHP, or TYI basal media, plus 8% PACSR (v/v), were inoculated with 10(3) trichomonads/ml from 3 strains (GT-3, GT-13, and GT-15) and incubated at 36.5 C for 72 hr. Depending on the strain, cultures grown in PEHP plus PACSR reached densities of 50% (GT-13), 63% (GT-3), or 82% (GT-15) as compared to controls grown in PEHPS. On the other hand, yields of GT-3, GT-13, and GT-15 maintained in TYI plus PACSR were, respectively, 53%, 57%, and 67% among those of cultures grown in TYI-S-33. In all experiments, PEHPS and TYI-S-33 contained 8% bovine serum. Yields reached in PEHPS were 2.07+/-0.275 to 4.83+/-4.41 x 10(6) trichomonads/ml, whereas in TYI-S-33, densities were 1.68+/-0.315 to 4.16+/-8.07 x 10(6) trichomonads/ml. In conclusion, PACSR added to PEHP or TYI media is useful for axenic cultivation of T. vaginalis in the absence of serum or bovine serum albumin. PACSR could be useful in performing analyses of biological properties that are inhibited by serum or any of its components.