BACKGROUND: Striae distensae evaluation criteria have been recently described, but none is focused on objective striae assessment. With the purpose of better and objectively estimating the severity of striae distensae, the Objective Stretch Marks Assessment Scale has been developed by the authors' team. METHODS: Seven hundred White patients were included in the study and assessed. To assess the severity of striae distensae, abdomen, breasts, hips, gluteal area, back area, thighs, calves, and upper limbs photonumeric grading scales were developed. The Rasch model was used as part of the validation process. A score was attributed to each patient, based on the scales we developed. The interrater reliability and test-retest reliability were analyzed. RESULTS: Eight photonumeric scales for striae distensae treatment outcomes assessment were developed. All scales exceeded criteria for acceptability, reliability and validity. The interrater and intrarater reliabilities were good, with a substantial or virtually perfect interrater reliability for the total score (P = 0.16). CONCLUSIONS: The authors' results allowed them to validate the Objective Stretch Marks Assessment Scale as a reliable and reproducible tool to assess striae distensae treatment outcomes. This scale could be also considered as an important new metric that can be used in clinical research.