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cantly associated with the count of days worked by month during the second year of follow-up (IRR=1.01; 95% CI=1.00, 1.02). A crude interpretation of this IRR would be that for every 30 days of abstinence in year 1, a person in 1 of the substance dependence groups would have 9% more employment days per month than would someone who was not abstinent. When examined as a time-varying covariate, previous month employment was significantly associated with the number of days worked in the following month (IRR=1.43; 95% CI=1.25, 1.60). Figure 3 depicts abstinence rates among those who worked each month within the substance-dependent groups. These results suggest 2 observations. First, those working in the ICM group showed a trend of increasing abstinence over time, whereas the trend for those in usual care was relatively flat. Second, by the end of the follow-up period, more than three fifths of the ICM participants who were working were also abstinent, whereas approximately one third of the working participants in usual care were completely abstinent. DISCUSSION Our findings provide support for the effectiveness of ICM in increasing rates of longerterm abstinence and employment among drugdependent women receiving TANF when compared with those in the screen-and-refer model. Group differences in abstinence rates during the past 9 months of follow-up (months 16-24) significantly widened, with clients in usual care, on average, having lower rates at month 24 compared with month 15 and those in ICM having higher rates. In month 24, abstinence rates in ICM (47%) were almost twice those in usual care (24%). Significant employment effects for ICM emerged during employment indicator-full-time employment-during months 23 and 24 ranged from an OR of 1.7 to an OR of 3.2. In addition, early abstinence significantly predicted later employment. As we noted in a previous article, a number of study features (e.g., random assignment, excellent follow-up rates) strengthen study internal validity.9 Importantly, the control group-screen and refer-is the standard of care in many welfare settings and not an artificially weak comparison. Interpretation Results showing that the magnitude of ICM effects do not weaken through 24 months are consistent with earlier findings of ICM benefits over the first 15 months of follow-up, even though the most-intense case management and treatment activities occurred during the first 3 months of the intervention.9 The strengthening of effects found during the past 9 months was not hypothesized but is intriguing. It may be that case managers help clients to avert crises and relapse via the availability of monitoring and flexible provisionof services outside thecontext of formal treatment. In addition, it may be that abstinence and employment have a reciprocal reinforcing influence. This explanation is consistent with the apparent concurrent acceleration of rates of abstinence and employment in ICM after month15. We intend to examine these possibilities in subsequent analyses. Findings indicate that the usual care group actually had higher rates of employment than did the ICM group during the first year of follow-up, but the relationship reversed during year 2. In addition, post hoc analyses suggested that the strongest group differences were in rates of full-time employment. These findings are consistent with earlier ones indicating that ICM participants were significantly more likely than were usual care participants t