National Jewish population surveys in the U.S. provide comprehensive data and insights about the Jewish community's development. Controversy accompanied the 2000-01 NJPS since inception and through release of the final report. This paper focuses on the plausibility of Jewish population size - namely, a decline since 1990 - as estimated from the 2001 NJPS. While the size of the U.S. Jewish population is difficult to assertain, growth momentum reached its peak around 1990, followed by moderate decline. Population aging and a decline in the wish to identify as a Jew underlie a decrease in the Jewish population. In retrospect, the 1957 Current Population Survey and 1990 NJPS probably better represented the total Jewish population, while the 1970 NJPS and 2001 NJPS better covered the more Jewishly identified sections. NJPS 2001, in any case, is an important and usable source.