Power systems require a wide range of ancillary services in order to function and renewables will be expected to provide such services in line with their increasing penetration. This paper focuses on the participation of wind energy in response and reserve markets. We compare the present situation in Great Britain (GB) and Spain, and make recommendations to support future development. Wind is already participating in a limited range of ancillary services in both countries: frequency response in GB and reserve services in Spain. We analyse the effects of market design, subsidy arrangements, and systemspecific needs on participation of wind in these markets, and then make policy recommendations designed to enable increased participation from wind. Our recommendations include the use of short-term markets to enable the use of accurate wind power forecasts, capacity-based subsidy schemes to avoid distorting ancillary service markets, and facilitating the participation of aggregated (single and mixed technology) resources. Country-specific recommendations include revising the current settlement process in GB to remove the incentive to over-estimate short-term generation forecasts, and establishing a competitive frequency containment reserve market in Spain. These recommendations are supported by analysis of publicly available market data.