The use of lactic acid bacteria (LAB) as vaginal probiotic cultures depends on the preservation technologies employed by the related industries. A full two-factor analysis of variance (ANOVA), considering medium and strain, of the decrease in bacterial viability during freeze-drying was applied. Lactobacillus gasseri CRL1421 was significantly more resistant than L. gasseri CRL1412 to the process. L. gasseri CRL1412 suspended in skim milk showed a significantly higher resistance than when it was suspended in water, but lactose or sucrose did not significantly increase its viability after lyophilization. Lactobacillus delbrueckii subsp. delbrueckii CRL 146 1, an autoaggregative strain, was significantly more sensitive to freeze-drying under the assessed conditions. The dried cultures were included in two pharmaceutical forms and viability was monitored during 270 days of storage. Although the microorganisms studied belonged to the same species, the optimal storage conditions were different for each of them. Our results can be applied to the design of a veterinarian probiotic to prevent metritis in diary postpartum cows. (C) 2007 Elsevier Ltd. All rights reserved.