The effect of two different disinfectants on the dimensional stability of two alginate impression materials over five days was investigated. 60 impressions were made under standardised conditions, 30 with each alginate, of which ten were disinfected in each disinfectant and ten were controls. Impressions were stored over a period of five days in a container with 100% humidity. Measurements were made between four points. Two-way analysis of variance indicated no differences in the change from baseline to day 5 between any of the combinations of alginate and disinfectant. Only two of the changes between baseline and day 5 reached statistical significance at the p < 0.01 level. Therefore it can be concluded that within the limitations of this study when newer alginate impression materials are disinfected they remain stable over 5 days.