The major aim of the current study was to demonstrate that preexperimentally established verbal functions can be examined, and transferred to arbitrary stimuli, using the procedures adopted by relational frame theory. Ten subjects were first exposed to relational pretraining, similar to that employed by Steele and Hayes (1991), in order to establish the relational functions of SAME, OPPOSITE, and DIFFERENT in three arbitrary stimuli. Subjects were then trained in the following relations: SAME/S1- DOMINATE, DIFFERENT/S1-FORGET, OPPOSITE/S1-SUBMIT, SAME/S1-X1, DIFFERENT/S1-X2, and OPPOSITE/S1-X3. Testing involved presenting the subjects with PENIS or VAGINA as samples and X1, X2, X3, and a question mark as comparisons (subjects were instructed to choose the question mark if they felt that none of the other comparisons were correct). All subjects consistently chose X1 given PENIS in the presence of SAME but X3 in the presence of OPPOSITE. Similarly, they chose X3 given VAGINA in the presence of the SAME contextual cue, but chose X1 in the presence of OPPOSITE. Four of the ten subjects chose X2 in the presence of DIFFERENT, given either PENIS or VAGINA as a sample. The six remaining subjects chose the question mark on these tasks, thus indicating that the relation between X2 and PENIS was unspecified. Five of the subjects were exposed to an additional test in which AMNESIA was presented as a sample. In the presence of SAME, three subjects consistently chose the question mark, whereas two subjects consistently chose X2. In the presence of DIFFERENT, subjects consistently chose either X1 or X3. Finally, in the presence of OPPOSITE, subjects consistently chose the question mark. These data support a relational frame account of sexual categorization.