The governments of many developed economies are facing policy issues associated with ageing populations. Pension reforms, increasing labour force participation of older workers and increasing the standard retirement age are policy reforms suggested by the OECD to address ageing populations. However, many of the same governments now embracing these reforms had until recently encouraged early exit of older workers from the labour force in periods of excess labour supply, leading to allegations that these governments had treated older workers as a ―reserve army of labour‖. In this paper a panel model is estimated for the labour force participation of males aged 55-59 and 60-64 years in 21 OECD countries as a function of social security generosity and labour market variables using biennial data covering the time period 1961 to 2003. The findings emphasise the role of the labour market variables over social security generosity for explaining older worker labour force participation trends. This implies that OECD governments will now struggle to mobilise older workers as a reserve army of labour in response to ageing society pressures through pension policy reform alone without addressing the role of the aggregate labour market.