Minors' access to alcohol and tobacco is a major public health concern because of the many deaths and disabilities associated with use and the ease with which minors purchase these products. We evaluated the effects of a community-based substance abuse coalition's efforts to reduce alcohol and tobacco products to minors. The intervention - implemented entirely by coalition members - consisted of adults and minors issuing citations to clerks in supermarkets, convenience stores and liquor stores, who were willing to sell alcohol and tobacco products to minors and issuing commendations to clerks who refused to sell. For those liquor stores receiving the citizen's surveillance, there was a marked decrease in alcohol sales to minors, from 83% to 33%; and in those liquor stores not experiencing the intervention, there was a smaller decrease in alcohol sales, from 45% to 36%. This study's findings suggest that citizen surveillance and feedback may be effective in reducing alcohol sales to minors when the intervention is fully implemented, but may be ineffective, at least in these doses, with tobacco sales.