OBJECTIVES: To assess the association between self-perceived copay burden and medication adherence among patients with schizophrenia. METHODS: Data were collected from December 2007 to February 2008 from a web-based consumer panel. Adults (age 18+) self-reporting a diagnosis of schizophrenia were invited to participate in the study through self-reported questionnaires on both the internet and through 43 interview facilities across the US. Inclusion criteria for analysis were: current use of an SGA, and no exposure to clozapine or a depot formulation antipsychotic. Adherence was assessed using the MMAS, with general adherence defined as MMAS<2, and complete adherence defined as MMAS<1. Logistic regression models were developed to assess the effects of self-perceived copay burden on adherence while adjusting for demographics, substance use, concomitant psychotropic medications, comorbidities, and health insurance. RESULTS: Of the 351 study respondents who met the criteria for analysis, 39% (n=137) perceived experiencing burden from their medication copays. Adjusting for covariates, the effects of copay burden on general adherence approached but did not reach significance (p=0.060). However, patients who experienced a copay burden were less than half as likely to have complete adherence [OR=0.427; 95% CI: (0.257, 0.711); p=0.001]. Effects of copay burden on the individual components of the MMAS varied. Patients with copay burden were more likely to forget to take medication [OR=2.058; 95% CI: (1.270, 3.335); p=0.003] and to discontinue medication when feeling worse [OR=2.000; 95% CI: (1.140, 3.507); p=0.016]. Being careless about taking medication and discontinuing medication when feeling better were not significantly affected by copay burden. CONCLUSIONS: Among patients with schizophrenia using SGAs, copay burden is associated with forgetting to take medication, discontinuing medication when feeling worse, and lesser likelihood of complete adherence. Less restrictive formularies that reduce copay burden for SGAs may have a positive effect on medication adherence among patients with schizophrenia.