This research uses population-based administrative data linking health service use to longitudinal postal code information to describe the residential mobility of individuals with a severe mental illness (SMI), schizophrenia. This group is compared to two cohorts, one with no mental illness, and one with a severe physical illness of inflammatory bowel disease. The percentage of individuals with one or more changes in postal code in a 3-year period is examined, along with measures of rural-to-rural regional migration and rural-to-urban migration. Demographic, socioeconomic, and health service use characteristics are examined as determinants of mobility. The odds of moving were twice as high for the SMI cohort as for either of the other two cohorts. There were no statistically significant differences in rural-to-rural or rural-to-urban migration among the cohorts. Marital status, income quintile, and use of physicians are consistent determinants of mobility. The results are discussed from the perspectives of health services planning and access to housing.