The temperament constructs of low positive affectivity (PA) and high behavioral inhibition (BI) overlap and are often not differentiated in the research literature. In particular, both constructs are characterized by low approach and engagement. However, current theoretical conceptualizations of these constructs suggest that low PA should be associated with low approach across most contexts, whereas BI should be associated with low approach only in novel situations. The present study used laboratory measures of child temperament and behavior to test these hypotheses in a sample of 100 preschool-age children. Results indicated that in novel situations, both lower positive affect and higher BI predicted low behavioral approach. However, in non-novel situations, only lower levels of positive affect predicted lower levels of approach; BI was not related to approach behavior in more familiar contexts. In conclusion, this study indicates that the overlap between the temperament traits of low PA and high BI is limited to novel contexts and that these constructs are distinguished by behavior in non-novel situations.