Never-married persons (singles) constitute a growing demographic group; yet, the magnitude of the all-cause relative mortality risk for nonelderly singles is not known and important moderating factors have not been explored. The authors used meta-analysis to examine 641 risk estimates from 95 publications that provided data on more than 500 million persons. The comparison group consisted of currently married individuals. The mean hazard ratio for mortality was 1.24 (95% confidence interval: 1.19, 1.30) among multivariate-adjusted hazard ratios with a high subjective quality rating. Meta-regressions showed that hazard ratios have been modestly increasing over time for both genders, but have done so somewhat more rapidly for women. The results also showed that the hazard ratio decreased with age and that study quality has an important relation to hazard ratio magnitude.