Objective To evaluate the impact of the 2006 Massachusetts health reform, the model for the Affordable Care Act, on short‐term enrollment and utilization in the unsubsidized individual health insurance market. Data Source Seven years of administrative and claims data from Harvard Pilgrim Health Care. Research Design We employed pre‐post survival analysis and an interrupted time series design to examine changes in enrollment length, utilization patterns, and use of elective procedures (discretionary inpatient surgeries and infertility treatment) among nonelderly adult enrollees before (n = 6,912) and after (n = 29,207) the MA reform. Principal Findings The probability of short‐term enrollment dropped immediately after the reform. Rates of inpatient encounters (HR = 0.83, 95 percent CI: 0.74, 0.93), emergency department encounters (HR = 0.85, 95 percent CI: 0.80, 0.91), and discretionary inpatient surgeries (HR = 0.66 95 percent CI: 0.45, 0.97) were lower in the postreform period, whereas the rate of ambulatory visits was somewhat higher (HR = 1.04, 95 percent CI: 1.00, 1.07). The rate of infertility treatment was higher after the reform (HR = 1.61, 95 percent CI: 1.33, 1.97), driven by women in individual (vs. family) plans. The reform was not associated with increased utilization among short‐term enrollees. Conclusions MA health reform was associated with a decrease in short‐term enrollment and changes in utilization patterns indicative of reduced adverse selection in the unsubsidized individual market. Adverse selection may be a problem for specific, high‐cost treatments.