Preparation of instructors is considered to be one of the greatest needs in adult basic education (ABE) and English-as-a-Second Language (ESL) programs. Many ABE and ESL teachers and volunteer instructors receive little or no training, either in subject matter content or in the process of teaching English to adults. The challenge for the adult education field is to design an effective system of staff development within the constraints of the ABE and ESL delivery system. These constraints include limited financial resources for programs, the part-time nature of instruction for adults, high instructor turnover, few state training requirements for ABE and ESL instructors, and lack of a unified adult education research base. This digest summarizes research on the formats of staff development for ABE and ESL teachers and volunteer instructors and identifies key elements of effective staff development programs. (VWL)