Previous studies comparing groups of subjects have indicated differential probabilities of stimulus equivalence outcome as a function of training structures. One-to-Many (OTM) and Many-to-One (MTO) training structures seem to produce positive outcomes on tests for stimulus equivalence more often than a Linear Series (LS) training structure does. One of the predictions from the discrimination analysis of R. R. Saunders and Green (1999) is that the differences in outcome between training structures should increase with number of class members. The purpose of the present experiment was to replicate and expand earlier findings on the effect of training structures and the stimulus equivalence outcome in a single-subject design. We wanted to compare the stimulus equivalence outcome in three 3-member classes to the outcome in three 4-member classes. In addition, we included all trial types in the tests and also changed the density of feedback before testing. The results from the current study replicated some earlier findings and showed that OTM gave a slightly better outcome on the stimulus equivalence test than MTO, and that both gave better outcome than LS. Thus, we did not find that MTO was superior to OTM with increasing number of members in each class. Reaction time data also replicated earlier findings that showed an increase from baseline to testing, and a more pronounced increase in reaction time on equivalence than symmetry trials. Differential procedural issues and some contingencies that could be important in understanding the results are discussed. (Contains 4 figures and 9 tables.)