In Britain about 10 per cent of workers have a second job. Possible motives for holding a second job are hours constraints in the first job or diferent utilities derived from the first and second job. Alternatively second job holding may reflect hedging behaviour in an uncertain environment. The holding of a second job may be triggered by changes in family circumstances or negative financial shocks. We describe the dynamics of of second job holding in Britain during the 1990s using panel data from the BHPS. Our results indicate that second job holding is surprisingly persistent over time. Negative financial shocks trigger second job holding but second jobs are not a measure to smooth labour supply over time. Hours constraints are of lesser importance in motivating second job holding that heterogeneous job characteristics.