We evaluated the effects of fixed-interval (FI), fixed-time (FT), and conjoint (combined) FI FT reinforcement schedules on the responding of 3 adults who had been diagnosed with schizophrenia. Responding on vocational tasks decreased for 2 of 3 participants under FT alone relative to FI alone. Responding under FI FT resulted in response persistence for 2 of 3 participants. Results have implications for the maintenance of desirable behavior, as well as for situations in which FT treatment has been implemented for problem behavior and problem behavior is nevertheless reinforced by caregivers.Key words: conjoint schedules, noncontingent reinforcement, time-based schedules, schizophrenia, vocational skillsFixed-time (FT) schedules involve the delivery of a stimulus independent of behavior after a set period of time has elapsed (Catania, 1998). Applied studies on FT reinforcement schedules have focused primarily on the treatment of problem behavior (e.g., Vollmer, Iwata, Zarcone, Smith, & Mazaleski, 1993). However, research findings also have suggested some conditions under which FT schedules might support response maintenance (e.g., Dozier et al., 2001;Ringdahl, Vollmer, Borrero, & Connell, 2001). Although timebased schedules have been a topic of considerable study, their effects on performance when combined with other schedules have received relatively little empirical attention. In the natural environment, it is unlikely that any simple schedule occurs in isolation. Rather, schedules that operate in the natural environment are likely to be a blend of simple and complex schedules (Nevin, 1998).In one of the first studies of combined response-dependent and response-independent schedules, Lattal and Bryan (1976) exposed the key pecking of three pigeons to a fixed-interval (FI) reinforcement schedule, in which the first response that occurred after a specified period of time had elapsed produced a reinforcer. Next, the previously evaluated FI schedule was accompanied by an FT schedule that was denser than the FI schedule. The behavior of some subjects decreased when both FI FT schedules were in place, whereas the behavior of others increased relative to when the FI schedule was implemented alone. Both outcomes are relevant to at least two clinical scenarios. First, the response increases observed by Lattal and Bryan suggest that combining FI and FT schedules might be a useful clinical strategy to maintain appropriate behavior. Alternatively, the response decreases suggest that treatments involving FT schedules, designed to decrease behavior, might remain effective even if behavior is intermittently reinforced. Given the relevance of conjoint FI FT outcomes and the inconsistent outcomes reported by Lattal and Bryan, the present study was designed to further evaluate them with a clinically relevant human population.