This mix of state and private pension provision in the United Kingdom provides a rare degree of variation in pension incentives for retirement. Using a sample of individuals from the UK Retirement Survey, the paper models the probability of retirement in terms of the incentives underlying the individual's pension plan as well as other socio-economic factors. It follows an option value approach and allows a separate role for pension wealth, for spouse's economic characteristics and for demographic characteristics. It distinguishes between SERPS and private schemes and models eligibility to disability. The results point to significant retirement incentive effects from the pension system.