The present article discusses how events outside a subject's skin and not accessible to another subject but to an experimenter may contribute to experimental analyses of private events. Of 16 undergraduates, 8, referred to as instructors, first learned conditional discriminations (i.e., B1C1, B2C2, B3C3, and B4C4) in a standard matching-to-sample (MTS) task with the stimuli Bs as the samples and the stimuli Cs as the correct comparisons. Then the other 8 subjects, learners, were exposed to modified MTS trials in which responses of the learners were reinforced or punished not by the experimenter but by the instructors. Conditional discriminations to be established were A1C1, A2C2, A3C3, and A4C4, in which the sample stimuli As were presented simultaneously with the stimuli Bs so that the instructors could not see the As but only the Bs. For 2 of the 8 pairs, the learners learned the AC conditional discriminations from the instructors who were not accessible to the stimuli As. Functionally, private events have been defined by their accessibility rather than their structure (e.g., Skinner, 1953). In this context, therefore, the stimuli As may be characterized as a kind of private events within the present 2 pairs of instructors and learners. (Contains 1 table and 3 figures.)