Background: Earlier studies show that 30-92 % of ACL reconstructed return to their pre-injury physical activity. It is not clear why some people do not return. Purpose: The purpose of this study was to investigate the return rate to pre-injury sport among ACL reconstructed men. Another purpose was to characterize those patients who return and those who do not. Metod: A Web-based questionnaire with questions about returning to physical activity was sent out during the spring of 2012 to 93 men who had undergone an ACL reconstruction 6-40 months earlier and who, after 6-40 months after surgery, were evaluated with validated strength tests and self-assessment outcome measures. Results: At 12 months after surgery 56 % of the subjects had returned to their pre-injury sport. If the criteria were set higher “back to the same- or a higher level” 14 % had returned. No differences were observed between those who had returned and those who did not, in terms of results on strength tests and the self-assessment outcome scores. Two years after surgery the subjects who returned to their pre-injury physical activity maintained a higher physical activity level compared to subjects that did not return. Conclusion: 56 % of the men that had undergone an ACL reconstruction reported that they returned to their pre-injury sport, but not to the same level, 12 months after surgery. Those men who returned maintained a higher physical activity level two years after surgery compared with those men who did not return.   Keywords: ACL, surgery, muscle function, self-efficacy, quality of life.   Level of evidence: II, retrospective study with prognostic value.