Population aging patterns: the expansion of mortality. We used the hypothesis of mortality compression as a framework to examine patterns of mortality from 1962 to 1984. Data from national vital statistics records were used for analysis of the changing age at death for percentiles of the population. Data from the Social Security Administration and the U.S. Census Bureau were used to calculate the force of mortality. The mean age at death for all percentiles, including the oldest groups, has risen during the interval. Examination of the coefficient of variation for the mean age at death suggests that there is a relative increase in the variability of age at death among the oldest old. The available data do not fit a hypothetical sequence of normal density distributions with an increasing mean and declining standard deviation. The force of mortality in those over 85 years appears to be decreasing in a pattern similar to that for those under 85 years. Current mortality patterns suggest an "expansion," rather than compression, of mortality at the oldest ages. Further refinement of these observations, with improved data on mortality among the oldest old, will be helpful in delineating mortality patterns. 