The University of Illinois at Chicago Library of the Health Sciences has taught end-user classes on the MEDLARS system since early 1985. Registration, class composition, and, most importantly, class organization evolved continuously during the first year of operation. Several feedback mechanisms were used. An examination of the past training and specialization of participants helped to determine teaching examples and pace; a more varied group of participants necessitated a broader range of examples and increased explanations. Participant evaluation forms and oral comments helped define scheduling, agenda, and the need for additional equipment and practice time. Further evaluation will center on the searching done by the program's alumni.