Seventy patients met our inclusion criteria in this retrospective study, all with an arthroscopic/arthrotomic-verified isolated total anterior cruciate ligament (ACL)-rupture and a minimum follow-up period of 3 years and no associated lesions. Due to emigration/death, 3 patients were not available for follow-up. Of the remaining 67, 25 patients underwent secondary ACL-reconstruction, equivalent to a failure rate of the initial non-operative treatment of 37%. All patients were initially treated conservatively. This left 42 patients for follow-up--9 answered a questionnare and 33 went through follow-up examination after a median of 7.1 years (range 3.3 14.6) including IKDC-evaluation form, Lysholm & Tegner score, ES-SKA-score, clinical examination and Stryker Laxity test. In the present study all values represent the 33 patients available for follow-up. Soccer, handball and alpine skiing were most frequently responsible for the injury. We observed in the 33 patients a decline in median Lysholm score from 100 (90-100) pretraumatic to 86 (42-100) at follow-up, and a decrease in median Tegner values from 7 (3-9) pretraumatic to 5 (2-7) at follow-up. All but 2 patients demonstrated a decline in Lysholm score, and only 3 patients returned to their preinjury level. According to the ESSKA-classification, the number of "cutting-sports performers" declined dramatically from 24 to 2. All but one patient ascribed their decline in activity to their knee status. The Stryker-measured AP-translocations were significantly higher on the injured knee (7.27) compared to the healthy knee (4.80) (P < 0.05). Intermittant rest pain was suffered by 63% of the patients. During the time from inclusion until follow-up, 13 (39%) patients sustained an additional ipsilateral knee lesion, most commonly a tear of the medial meniscus. The overall outcome was expressed in a low frequency of return to unrestricted preinjury level of function, and a high level of instability complaints resulting in many secondary ACL-reconstructions. Naturally some have adapted to their ultimate functional disability, but only through modification of activities, and the overall outcome after conservative therapy of these ACL-ruptures was not satisfactory.