Wallace Craig's "Appetites and Aversions as Constituents of Instincts," one of the seminal articles in animal behavior, comparative psychology, and ethology, appeared 100 years ago this year. The influence of this classic article is continuing and perhaps even expanding. Here we review the major ideas Craig offered in the article, provide a brief sketch of his scientific career and historical context, and examine the impact of the article on ethological and instinct theory. We also review some current applications of his work in diverse areas and discuss why it is cited more now than in earlier decades, especially in articles on causal mechanisms. (PsycINFO Database Record (c) 2018 APA, all rights reserved).