The hundreds of lake associations in Minnesota are examples of voluntary collective action organizations. Although these groups are organized for several purposes, their main concern is environmental management and specifically the improvement or preservation of lake water quality. Social capital probably affects organizational effectiveness. Survey and biophysical data were used to examine the determinants and efficacy of social capital in lake associations. Social capital production in lake associations was associated with water quality, lake size, recreational preferences, seasonality of residents, location, information sharing, per caput budget and relations with local government. Social capital also had a significant but small positive relationship with lake water clarity. Natural resource policy makers might consider investments in social capital as part of their strategy portfolio. Although statistical analyses of the role of social capital in local environmental management using large sample sizes are promising, several measurement and methodological difficulties remain.