Recent studies suggest that children are completing toilet training much later than the preceding generation. Our objective was to identify factors associated with later toilet training. Children between 17 and 19 months of age (n=406) were enrolled in the study. At enrollment, parents completed the Parenting Stress Index and the Receptive-Expressive Emergent Language Scale. Follow-up parent interviews were conducted every 2 to 3 months until children completed daytime toilet training. Information obtained at follow-up interviews included steps parents were taking to toilet train their child, child toilet training behaviors, presence and frequency of constipation, birth of a sibling, and child care arrangements. In a stepwise linear regression model predicting age at completion of toilet training, 3 factors were consistently associated with later training: initiation of toilet training at an older age, presence of stool toileting refusal, and presence of frequent constipation. Models including these variables explained 25% to 39% of the variance in age at completion of toilet training. In conclusion, a later age at initiation of toilet training, stool toileting refusal, and constipation may explain some of the trend toward completion of toilet training at later ages.