OBJECTIVE: To assess the level of participation of endocrinologists in the United States in the 2009 to 2010 H1N1 vaccination campaign and explore their perspectives on H1N1 vaccination. METHODS: We conducted a cross-sectional, mailed survey of a national sample of 1,991 endocrinologists in June through September 2010. The extent of the response and the survey responses are reported and analyzed. RESULTS: The overall response rate was 59%. The majority of endocrinologists strongly recommended H1N1 vaccine for children, whereas about a third did so for both nonelderly adults and seniors. Just over half (52%) of the responding endocrinologists had agreed to participate in the 2009 to 2010 H1N1 vaccine campaign and received vaccine, in comparison with 73% who offered seasonal influenza vaccine. The supply of H1N1 vaccine was a significant challenge, but otherwise endocrinologists reported few major problems with administration of H1N1 vaccine. Overall, less than half of the respondents thought that they would be "very likely" to provide vaccine in the event of a future influenza pandemic, with a much higher proportion among those endocrinologists who offered seasonal influenza vaccine and H1N1 vaccine. CONCLUSION: Although the experiences of endocrinologists who provided H1N1 vaccine were generally positive, many did not offer the vaccine and indicated that they are hesitant about providing vaccine during a future influenza pandemic. Approaches to increase their participation in future pandemics in an effort to reach persons at high risk for influenza and its complications, such as those with diabetes, should be further explored.