Background and purpose: Physical mechanisms are the possible factors involved in the development and maintenance of long-term handicaps after acute whiplash injury. This study prospectively examined the role of active neck mobility, cervical and extra-cervical pains, as well as non-painful complaints after a whiplash injury as predictors for subsequent handicap. Methods: Consecutive acute whiplash patients (n = 688) were interviewed and examined by a study nurse after the median of 5 days after injury, and divided into a high- or a low-risk group by an algorithm based on pain intensity, number of non-painful complaints and active neck mobility [active cervical range of motion (CROM)]. All 458 high-risk patients and 230 low-risk patients received mailed questionnaires after 3, 6 and 12 months. Two examiners examined all high-risk patients (n = 458) and 41 consecutive low-risk patients at median 11, 109, 380 days after injury. The main outcome measures were: handicaps, severe headaches, neck pain and neck disability. Results: The relative risk for a 1-year disability increased by 3.5 with initial intense neck pain and headaches, by 4.6 times with reduced CROM and by four times with multiple non-painful complaints. Conclusion: Reduced active neck mobility, immediate intense neck pain and headaches and the presence of multiple non-painful complaints are the important prognostic factors for a 1-year handicap after acute whiplash.