This study describes a contingency management intervention applied in group
treatment. In an HIV drop-in center, groups were held on Tuesdays and Thur
sdays for 35 weeks. An ABB ' CA design was used, in which reinforcers were
available in non-A phases. In the initial B phase, reinforcers were availab
le only on Tuesdays, and they switched to Thursdays in the B ' and C phases
. The reinforcer was a drawing that was associated with the possibility of
winning a prize. Reinforcers were provided for attending group and completi
ng steps related to treatment goals. The number of drawings escalated with
weeks of consecutive attendance and activity completion in the B phases, in
the C phase; a fixed number of draws were provided. Overall, the procedure
increased attendance, with an average of 0.7 clients (range 0-4) per sessi
on in the initial baseline phase to an average of seven clients (range 2-12
) during reinforcement phases. The percentage of activities completed also
rose from 25% during baseline to 65% during reinforcement phases. These dat
a suggest the feasibility of a group-based contingency management intervent
ion. d (C) 2001 Elsevier Science Inc. All rights reserved.