Objectives. To develop and validate an Objective Structured Assessment of Technical Skills (OSATS) scale for vacuum extraction. Design. Two part study design: Primarily, development of a procedure-specific checklist for vacuum extraction. Hereafter, validationof the developed OSATS scale for vacuum extraction in a prospective observational study. Setting. Rigshospitalet, University Hospital of Copenhagen. Population. For development an obstetric expert from each labor ward in Denmark (28 departments) were invited to participate. For validation nine first-year residents and ten chief physicians with daily work in the obstetric field were tested. Methods. The Delphi method was used for development of the scale. In a simulated vacuum extraction scenario first-year residents and obstetric chief physicians were rated using the developed OSATS scale for vacuum extraction to test construct validity of the scale. Main outcome measures. Consensus for the content of the scale. To test the scale Cronbachs alpha, interclass correlation and differential item function was calculated in the prospective study. Results. 89% completed the first and 61% completed the second Delphi round. Hereafter, consensus was obtained. There was a significant difference between residents´ and experts´ performance for total score and for the score of the separate parts of the scale. Cronbachs alpha for total score and for the separate parts of the scale was 0.91-0.95 and interclass correlation 0.84-0.9. Conclusions. The OSATS scale for vacuum extraction is a reliable test for differentiating between competence levels in a simulated setting.