Ill-health can inflict costs on households directly through spending on treatment and indirectly through impacting on labour productivity. The financial burden can be high and, for poor households, contributes significantly to declining welfare. We investigated socio-economic inequities in self-reported illnesses, treatment-seeking behaviour, cost burdens and coping strategies in a rural and urban setting along the Kenyan coast. We conducted a survey of 294 rural and 576 urban households, 9 FGDs and 9 in-depth interviews in each setting. Key findings were significantly higher levels of reported chronic and acute conditions in the rural setting, differences in treatment-seeking patterns by socio-economic status (SES) and by setting, and regressive cost burdens in both areas. These data suggest the need for greater governmental and non-governmental efforts towards protecting the poor from catastrophic illness cost burdens. Promising health sector options are elimination of user fees, at least in targeted hardship areas, developing more flexible charging systems, and improving quality of care in all facilities. The data also strongly support the need for a multi-sectoral approach to protecting households. Potential interventions beyond the health sector include supporting the social networks that are key to household livelihood strategies and promoting micro-finance schemes that enable small amounts of credit to be accessed with minimal interest rates.