The artificial sweetener saccharin is available in several forms, including pure saccharin (S) and saccharin sodium salt hydrate (SSSH). Acceptance and preference relative to 2% sucrose for these two forms was assessed using both older female and young male rats. At the higher of two concentrations, ∼0.4%, SSSH was more acceptable and more greatly preferred over 2% sucrose than was a similar concentration of S, whereas little difference between the two forms was detected at the lower concentration, ∼0.1%. These results indicate the importance for researchers of care in choosing and reporting the form of saccharin they use.