In the present work, several commercial polylactides (PLAs) have been rheologically characterized using both a parallel-plate and capillary rheometers. It has been found that PLAs with molecular weight, Mw, greater than a certain value, exhibit severe slip at the wall during capillary flow. The Mooney technique has been used to determine the slip of PLAs. The slip velocity was found to increase with decrease of Mw., a scaling also found for other polymers such as polyethylenes, polybutadienes and polystyrenes. The rheological and slip data has been used to formulate a K-BKZ constitutive equation to predict their rheology in capillary flow including the entrance pressure drop which was measured using capillaries of various diameters and lengths. Numerical simulations based on the K-BKZ constitutive model with slip at the wall gave a good representation of the experimental data and therefore it can be used for design purposes in the processing of PLAs.