Summary: It has been demonstrated that although the response in guinea pigs is variable, the polymers GLA5, GLT, GLPhe, GLA30, GLAT and GAT are antigenic. Both early (immediate) and late (delayed) skin reactions were noted. GLA30 and GLAT produced the most extensive reactions. From cross PCA reactions, it was determined that most of the specificity in GLA5, GLPhe and GLT is the same as in GL but that GLT also has a GT specificity. In GLA30 and GLAT, in addition to the above specificity, there is also a GA specificity.