Hand injuries are the main cause of work-related disability in young adults. We have devised the Modified Hand Injury Scoring System to quantify hand, wrist and forearm injuries. This study aims to determine its value in predicting ability and time taken to return to work after such injury. Prospectively-assigned MHISS at presentation was compared with demographic, injury, employment and quality of life information 40-52months after acute hand or forearm injury. MHISS score was the only variable investigated found to predict ability to return to work. Factors not associated included age at injury, occupation, hand injury side or dominance, main earner status and compensation-seeking. Median time to return to work increased from 30 to 760days for Mild and Major MHISS categories respectively. Injury severity quantified using MHISS is an important determinant of return to work after hand or forearm injury. Only 60% of patients return to work following a Major injury and may take over a year to do so. Such information may allow the patient to make early informed personal financial and retraining decisions after their injury.