“…To date, many parent training studies continue to be weakened by one of more of the following methodologica l problems: (1) small sample sizes, (2) lack of a control condition or nonrandom assignment to experimental groups, (3) inadequate use of follow-up to examine long-term maintenance of effects, (4) homogeneous samples, (5) poor attendance rates, and (6) high attrition rates (Barlow & Stewart-Brown, 2000;Thomas, 1999;Tucker & Gross, 1997). Nonetheless, several programs have documented ef cacy showing that, with some populations , they lead to signi cant improvements in parent-child outcomes that are sustainable up to at least one year post-intervention (Strayhorn & Weidman, 1991;Sutton, 1992;Tucker & Gross, 1997;Webster-Stratton, 1990). …”