With the purpose of developing a pattern alteration system for stretch fabrics, basic bodice pattern for knit was reduced in length and width. Nine different knits were used for the experiment. For each knit, six sleeveless shirts were made with patterns reduced in length and width by 6 different pattern alteration rates: 0%, 30%, 40%, 50%, 60%, or 70% of the stretch rate of the knits. The panel that was composed of 25 clothing specialists evaluated the fitness of the garments. The results of this study are as follows: The appropriate pattern alteration rate was different by the fabric stretch rate at wale and course. The different pattern alteration rate was needed at bust, waist, and hips. The knits with high stretch rate at course needed low alteration rate to have appropriate garment fit. The rib knits needed lower alteration rate than jersey or interlock to get the appropriate bodice width. The garment length was most appropriate at 20~30% of pattern length alteration rate.