The aim of this study was to retrospectively evaluate the safety and efficacy of polidocanol sclerotherapy in pain relief for painful venous malformations (VMs). Thirty-one patients with painful VMs underwent polidocanol sclerotherapy. Pain intensity was assessed with an 11-point verbal numerical rating scale. Sclerotherapy was technically successful in 58 (98.3%) of 59 sessions. Twenty-six (89.7%) out of 29 patients experienced an improvement in pain after sclerotherapy at follow-up, a mean of 46 months after treatment. The mean pain score improved from 6.6 + or - 2.5 before treatment to 2.4 + or - 2.9 after treatment (P <.001). The factors that significantly influenced the therapeutic effect were size of lesion (P = .008), margin of lesion (P = .006), and stasis of sclerosant (P = .032). Adverse events included hypotension and bradycardia during the procedure. No major complication occurred. Polidocanol sclerotherapy is safe and most efficacious in providing pain relief for patients with small VMs (equal to or less than 10 cm in diameter), VMs with a well-defined margin, and VMs with good stasis of sclerosant during sclerotherapy.