Quality circles (QCs) have been considered one of the most promising approaches to improving American workers' productivity. The differences of quality circle effectiveness between active QCs (N=36) and inactive QCs (N=17) in a 3-year period were examined in a quasi-experimental field study. The dependent variables examined were the amount of middle-management involvement, the number of people per quality circle (QC size), the attendance rate at QC meetings, and several measures of their problem-solving activities. The results suggested that active QCs had a significantly higher level of involvement from the middle management than had inactive QCs. Active QCs had more circle members and had a significantly higher attendance rate at QC meetings than had inactive QCs. Further, active QCs had a significantly lower rate of failure in their problem-solving process than had inactive QCs. It was also found that for active QCs, their QC tenure was negatively correlated with the QC size, and was positively correlated with the number of projects attempted, the number of projects dropped, and the number of projects completed. For inactive QCs, the attendance rate at AC meetings was negatively correlated with the number of projects completed and their QC tenure was negatively correlated with the rate of failure. (Author/NB)