A noted demographer assesses the reliability of data in the 1989 census of the Soviet Union for 14 regions of the Russian Federation affected by distortions designed by Soviet authorities to conceal the populations of “secret towns” of the military-industrial complex. More specifically, using declassified population data available but only selectively published following the disclosure of these hidden settlements (and their populations) in 1994, he re-estimates the urban populations of these regions in 1989, and compares differences in 1989–2002 population change indicated by use of the original and adjusted 1989 data sets. Distortions of up to 10 percent of the regional populations (and as high as 13 percent for their eponymous regional capitals) are examined in light of their implications for the calculation of a variety of demographic and population-based indicators in studies of Russia comparing the late Soviet and early post-Soviet periods.