Primary scientific literature seems not to be growing at a greater rate than the scientific community it serves. The impression of excessive proliferation arises mainly from the differentiation of journals to accomodate rapid expansion in specialized fields of research. A large fraction of this literature is of marginal value, but should not be excluded from comprehensive archives for possible retrieval. For awareness of significant current developments, however, scientists depend on a small number of core journals whose quality is maintained by editorial selectivity and competition.