Objective To evaluate the quality of controlled trials on 131I therapy for thyroglobulin positive and radioactive iodine negative metastases（131I WBS-/Tg+）. Methods We electronically searched MEDLINE (1966 to Mar. 2004), EMBASE (1984 to 2003), The Cochrane Central Register of Controlled Trial, CENTRAL (Issue 2, 2004), CBMdisc (1978 to 2004) and CNKI (1994 to 2004), and handsearched 5 radiotherapy and endocrinology journals (Jan. 1980 to Apr. 2003). The methodological quality of included studies was assessed by using quality assessment criteria of the Cochrane systematic review guideline. Results Three non-randomized controlled trials were included. One was historical controlled trial, and two prospective trials. The sample sizes of three trials were 26, 60 and 70 respectively without mentioning the calculation base. The comparability of baseline was mentioned but not comparable across the trials. No double blind studies were used in the assessment of 131I efficacy. The time of follow-up varied from 2 to 15 years. None studies mentioned the side effects of 131I therapy for 131I WBS-/Tg+ metastases. Only two studies applied statistical methods properly. Conclusions Problems about allocation of groups, double blind, sample size, and follow-up period continue to exist in published controlled trials. RCT or prospective controlled trials of high quality are urgently needed in order to define the efficacy and safety of 131I therapy for 131I WBS-/Tg+ metastases.