PURPOSE We determined the rate of patients lost to followup in level Ⅰ/Ⅱ evidence-based studies of surgical management of stress urinary incontinence in women.MATERIALS AND METHODS Randomized clinical trials(level Ⅰ)or nonrandomized but prospective studies(level Ⅱ)related to surgical treatment of stress urinary incontinence in women from January 1995 to November 2009 were searched on PubMed(R).Data reviewed included study type,number of participating centers or hospitals,sample size calculation,surgical techniques,power calculation,estimated dropout rate,followup duration,and rate of and reasons for loss to followup.RESULTS A total of 47 randomized clinical trials and 24 nonrandomized prospective studies,representing a total of 11,007 women,met study inclusion criteria.Of the articles 33 provided details on sample size calculation and 16 explained the lost to followup rate after contacting patients lost to followup by mail or telephone.The incidence of patients lost to followup was 8.1%(587 of 7,213)at 12 months or less in 58 articles,28%(813 of 2,890)at 24 months in 13,36%(248 of 694)at 36 months in 5,33%(233 of 708)at 36 to 60 months in 5 and 32.4%(722 of 2,227)at 60 months or greater in 10.A total of 11 articles reported no missing data due to small sample size or short followup.Only 7 articles defined cases lost to followup as treatment failures and reported outcomes accordingly.CONCLUSIONS In this contemporary literature review we found an important attrition rate of followup with time that directly affects the strength of the conclusions on the remaining patient population.