During the past two decades, union density has declined in the United States and employer provision of health benefits has changed substantially in extent and form. Using individual survey data spanning the years 1983–97 combined with employer survey data for 1993, the authors update and extend previous analyses of private-sector union effects on employer-provided health benefits. They find that the union effect on health insurance coverage rates has fallen somewhat but remains large, due to an increase over time in the union effect on employee “take-up” of offered insurance, and that declining unionization explains 20–35% of the decline in employee health coverage. The increasing union take-up effect is linked to union effects on employees' direct costs for health insurance and the availability of retiree coverage.