This article explores issues of scalability and sustainability in distance learning. The authors kept detailed records of time they spent teaching a course in geographic information science via the World Wide Web over a six-month period, during which class sizes averaged 49 students. The authors also surveyed students' satisfaction with the distance learning course through ratings and open-ended questions. Findings are compared with similar data collected a year earlier, when class sizes associated with the same distance learning course averaged 18 students. In response to the increase in average class size by a factor of 2.7, the authors' course-related workloads increased by a factor of about 2.5 (from 47.5 hours to 116.7 hours total). Analyses of student feedback suggest that student satisfaction with the course was high overall and suffered no significant decline as a result of increased instructional efficiency.