Objectives: Stroke is a major global disease that requires extensive care and support from society and relatives. The aim of this study was to identify and quantify the long-term informal support and to estimate the annual cost of informal support provided by spouses to their stroke surviving partner. Method: Data were based on the 7-year follow-up of the Sahlgrenska Academy Study on Ischemic Stroke. One-third of the spouses stated that they provided support to their stroke surviving partner. The magnitude of the support was assessed with a study-specific time-diary and was estimated for independent and dependent stroke survivors based on the scores of the modified Rankin Scale. To deal with skewed data, a two-part econometric model was used to estimate the annual cost of informal support. Result: Cohabitant dyads of 221 stroke survivors aged amp;lt; 70 at stroke onset were included in the study. Spouses of independent stroke survivors (n = 188) provided on average 0.15 hr/day of practical support and 0.48 hr/day of being available. Corresponding figures for spouses of dependent stroke survivors (n = 33) were 5.00 regarding practical support and 9.51 regarding being available. The mean annual cost of informal support provided for independent stroke survivors was estimated at (sic)991 and (sic)25,127 for dependent stroke survivor. Conclusion: The opportunity cost of informal support provided to dependent midlife stroke survivors is of a major magnitude many years after stroke onset and should be considered in economic evaluations of health care.