This article presents estimates of the proportion of the U.S. population that had mental health benefits in 1999, of the extent of their coverage, and of the proportion that were enrolled in health plans subject to the Mental Health Parity Act of 1996 (MHPA). Findings indicate that over three-quarters (76%) of the U.S. population had mental health benefits as part of their health insurance. Approximately 18% of the population had no mental health benefits, and for the remaining 6%, mental health benefits could not be determined. Of the 18% with no mental health benefits, most (84%) had no health insurance whatsoever, while the remainder (16%) had health insurance that did not cover mental health benefits. Estimates of the generosity of coverage indicate that 44% of the population had benefits that included prescription drugs, and that provided at least 30 inpatient days and 20 outpatient visits for psychiatric care. For 12% of the population, benefit generosity could not be determined. Finally, study results suggest that the MHPA affected only 42% of the U.S. population.