The long-term stability of social participation was investigated in a representative urban population of 415 men and 579 women who had taken part in the nationwide Mini-Finland Health Survey in the years 1978-1980 and were re-examined 20 years later. Stability was assessed by means of the following tracking coefficients: kappa, proportion of stability, Spearman correlation, and stability coefficient (odds ratio) for engagement in clubs and voluntary societies, cultural and sports attendance, congregational activity, outdoor and productive activity, cultural interests, and hobby activity. The tracking results showed fair to moderate stability for the above measures of social participation, varying from the highest weighted kappa (0.43) for congregational activity in women to the lowest weighted kappa (0.22) for cultural and sports attendance in men. Migration from rural to urban community did not affect the stability of social participation. The underlying latent construct "social participation" based on a two-wave multi-variable model showed good stability (r = 0.65). We conclude that social participation rests on a fairly stable foundation making it a useful tool for long-term epidemiological studies.