Eight maize (Zea mays L.) populations were developed cooperatively by the USDA-ARS and the Iowa Agriculture and Home Economics Experiment Station. The populations were developed as part of a larger breeding methods study conducted in the BSll maize population. Hallauer et al. (2) released BSll(FR)C2 after two cycles of full-sib reciprocal recurrent selection using BS10 as the tester population. Population BS1 I, originally designated as Pidneer Two-ear Composite, was developed by W.L. Brown at Pioneer Hi-Bred International by crossing southern prolific germplasm with U.S. Corn Belt lines (2). The main objective of the breeding methods study was to evaluate ¯ response to seven recurrent selection methods, after five cycles of selection, in a common base population. The study was unique, in that the responses to seven recurrent selection methods were compared in a common base population (BSll) by using the same selection intensity (20%) and the same effective population size (20) for all methods. A second objective of the breeding methods study was to evaluate the effect of population size on recurrent selection. Four effective population sizes (5, I0, 20, and 30) were studied by using the S1 recurrent selection method. The selection intensity was 20% for all effective population sizes, so the number of progenies evaluated varied from 25 to 150. For all recurrent selection programs, progenies were evaluated for 1 yr at three locations, with two replications per location. Selections were made on the basis ofa heritability index (3). Traits included in the index were grain yield, grain moisture, root lodging, and stalk lodging. Populations developed from the study are described below.