Abstract. Background: Here, we update an earlier systematic review on the preventive efficacy of active compression stockings in patients with diagnosed proximal deep venous thrombosis (DVT) by including the results of recently published trials. The aims are to synthesize the results of the original studies, and to identify details to explain heterogeneous results. Methods: We searched the Cochrane Library, PubMed, Scopus, and Medline for original studies that compared the preventive efficacy of active compression stockings with placebo or no compression stockings in patients with diagnosed proximal DVT. Only randomized controlled trials (RCTs) were included. Results: Five eligible RCTs with a total of 1393 patients (sample sizes ranged from 47 to 803 patients) were included. In three RCTs, patients started to wear compression stockings, placebo stockings or no stockings within the first three weeks after the diagnosis of DVT. The results of two RCTs indicate a statistically significant reduction in post-thrombotic syndrome (PTS) of 50% or more after two or more years. The result of one RCT shows no preventive effect of compression stockings at all. Due to the heterogeneity of the study results, we refrained from pooling the results of the RCTs. In a further RCT, randomization to groups with and without compression stockings took place six months after the diagnosis of DVT, and in another RCT, only patients with the absence of PTS one year after the diagnosis of DVT were analyzed. One RCT revealed a significant reduction in symptoms, whereas another RCT failed to show any benefit of using compression stockings. Conclusions: At this time, it does not seem to be justifiable to entirely abandon the recommendations regarding compression stockings to prevent PTS in patients with DVT. There is evidence favoring compression stockings, but there is also evidence showing no benefit of compression stockings.