BACKGROUND Marital status has been implicated as a prognostic factor in bladder cancer survival. However, few studies have explored potential mechanisms through which this might occur. METHODS The study identified 19,982 bladder cancer patients from the SEER-Medicare database (1992-8) and constructed sex-specific Cox proportional hazard models to assess the relation between marital status and 5-year survival, while sequentially adding covariates to test possible mechanisms. RESULTS Multivariable Cox analyses suggest that at every stage, married men had better survival than unmarried men independent of age, race, ecologic socioeconomic status, comorbidities, any or aggressive treatment (assessed separately), and accessing a teaching hospital (hazard ratio (HR) 0.80; 95% confidence interval (CI) 0.74 to 0.87). Among women with stages II-IV bladder cancer, age and the presence of comorbid conditions explained the association between marital status and survival. However, among those diagnosed with stage I bladder cancer, none of the covariates explained the association between marital status and decreased mortality (fully adjusted HR 0.72; 95% CI 0.62 to 0.84). CONCLUSIONS The lack of evidence of mediation through treatment, overall health, SES, or quality of healthcare institution among married men and women with stage I disease suggests they may be benefiting from something other than these factors, perhaps practical or social support.