Models of possible adjacent re-entry chain folds for the most stable form (form I) of syndiotactic polypropylene in the body-centered orthorhombic unit cell have been studied by molecular mechanics. Folds along (100), (010), and (110) planes connecting chains having both the same or the opposite chirality have been investigated. Various models of folds with different number of bonds have been built up and optimized by conformational energy calculations. Tight folds are the lowest in energy. Low-energy folds are possible along the three fold planes with some restrictions on the chirality of the chains. The energy values obtained for the best folds are in good agreement with the work of the fold deducible from experimental determinations. The energy calculations also indicate that configurational defects can be well tolerated in the fold.