The purpose of this paper is to report an audit of 2,437 downloads of the AIDA interactive educational diabetes simulator. AIDA is a diabetes computer program that permits the interactive simulation of plasma insulin and blood glucose profiles for educational, demonstration, and self-learning purposes. It has been made freely available, without charge, on the Internet as a noncommercial contribution to continuing diabetes education. Since its launch in 1996 over 200,000 visits have been logged at the AIDA Website-www.2aida.org-and over 37,000 copies of the AIDA program have been downloaded free-of-charge. This report documents an audit of downloaders of the software, with the intended goals of the study being to demonstrate the use of the Internet for auditing and surveying diabetes software users and to confirm the proportion of patients with diabetes and their relatives who are actually making use of the AIDA v4.3 program. The Internet-based survey methodology was confirmed to be robust and reliable. Over a 7 1 / 2 -month period (from mid-July 2000 to early March 2001) 2,437 responses were received. During the corresponding period 4,100 actual downloads of the software were independently logged via the same route at the AIDA Website-giving a response rate to this audit of 59.4%. Responses were received from participants in 61 countries-although over half of these (n 5 1,533; 62.9%) originated from the United States and United Kingdom. Of these responses 1,361 (55.8%) were received from patients with diabetes and 303 (12.4%) from relatives of patients, with fewer responses from doctors, diabetes educators, students, nurses, pharmacists, and other end users. This study has confirmed the feasibility of using the Internet to survey, at no real cost, a large number of medical software downloaders/users. In addition, it has yielded up-to-date and interesting data about who are the main downloaders of the AIDA program. 467