Essential for an effective criterion-referenced testing program is a set of test items that are "valid" indicators of the objectives they have been designed to measure. Unfortunately, the complex matter of assessing item validity has received only limited attention from educational measurement specialists. One promising approach to the item validity question is through the collection and analysis of the judgments of content specialists. The purpose of this paper are twofold: First, several possible rating forms and statistical methods for the analysis of content specialists' data are discussed. Second, the results of item validation work with science teachers and three of the more promising rating forms are presented. The overall results of the study clearly support the recommendation for expanded use of content specialists' ratings is the item validation process. (Author/RC)