A questionnaire survey on carpooling characteristics at a large suburban technical center in Warren, Mich. was carried out in early 1973. The survey showed that carpool participation increased with both trip time and trip distance. However, carpooling decreased for the longer trips where neighbor-coworker concentration was low. It was also found that larger carpools were composed of respondents with longer trip lengths. The overall results indicate that trip length and neighbor-coworker concentration are the two most important locational factors influencing carpool formation. Carpool participation has increased from 22% in early 1973 to 36% in early 1974. This change might be attributable to the fuel shortage, greater publicity, and carpool matching efforts.