Research provided a comprehensive descriptive analysis of the Iowa adult basic education (ABE) population. Data were collected through comprehensive interviews from a carefully drawn random sample (n=323) of those who completed less than 11 grades. A random subsample was followed up by telephone interview. The population was described on three dimensions: motivations for attending, sociodemographic characteristics predictive of group behavior, and learners' cognitive ability and achievement levels. The research also segmented the population into groups that represented the underlying behavioral structure of the population and determined the success of the population according to selected success indicators. Findings indicated an underlying structure to motivation that was embodied in 10 factors: self-improvement, family responsibilities, diversion, literacy development, community/church involvement, job advancement, launching, economic need, educational advancement, and urging of others. The ABE population segmented itself into six types: mainstream women, the least affluent/least employed, the urged, young adults, the climbers, and low ability strivers. The cognitive ability, aptitude, and achievement levels were quite low. (Instruments are appended.) (YLB)