Understanding the cognitive processes, skills and strategies that examinees use in testing is an important aspect of score interpretability. Both item responses and response times are increasingly available with computerized testing. Several item response theory models have been developed to incorporate response times into estimations of trait level; however, recent research has shown that examinees differ widely in response time patterns. This presentation will focus on the use of response times, in conjunction with explanatory item response theory models of item accuracy, provides information relevant to score interpretations. For many item types, mixture class IRT models identify latent classes of examinees with different processes, skill and strategies.