Adaptive Conjoint Analysis (ACA) is software for conjoint (trade-off) analysis. The term "adaptive" refers to the fact that the computer-administered interview is customized for each respondent. Data are analyzed as the interview progresses, and we choose questions likely to reveal the most about the respondent's values in the shortest time. ACA is classic conjoint technique first released in the 1980s. Although it was the most popular conjoint methodology during the 1990s, it is less often used today. This paper provides a description of the adaptive technique, including technical details.