Experimental evidence showed that the pH of a formalin solution stabilized with borax decreased during the fixation of fishes. A pH low enough to affect the calcium content of specimens was reached in some cases. Respondents to a survey on preservation practices indicated that most institutions attempted to neutralize the acidic nature of formalin and that borax was the most commonly used neutralizer. Test results indicate the need for a reevaluation of the use of borax in stabilized formalin pH during the fixation process.