Background: Mixed urinary incontinence (MUI) is a common, bothersome condition in women. In MUI, the two subtypes of urinary incontinence that coexist are treated differently; stress urinary incontinence (SUI) is primarily treated surgically while urge urinary incontinence (UUI) is primarily treated medically. There is no evidence to guide the treatment for women with significant bother from both incontinence subtypes. Therefore, investigators of the Urinary Incontinence Treatment Network (UITN) designed and initiated a randomized clinical trial comparing outcomes for two distinct initial treatment approaches for women with mixed urinary incontinence (MUI): therapy initiated with surgery versus therapy initiated with nonsurgical treatment. Purpose: The aim of this manuscript is to describe the challenges in planning and implementing this randomized clinical trial. Methods: The mixed incontinence: medical or surgical approach (MIMOSA) trial was designed as a practical or pragmatic clinical trial to establish the relative efficacy of two specific treatment approaches. The design presented many challenging decisions including: (1) selection of practical paradigm; (2) refining inclusion/exclusion criteria to offer equipoise; (3) selection of feasibility sample size; (4) recruitment challenges for two divergent treatment approaches (medical vs. surgical), and (5) resolution of ethical and methodological issues. Results: MIMOSA recruitment was planned in two phases, starting with a 5-month pilot and feasibility phase followed by a full trial contingent on the outcome of the first phase. The feasibility portion of the MIMOSA trial started in November 2008. 1198 subjects were screened and approached forstudy enrollment, but only 27 consented to randomization. The feasibility study was halted due to lack of enrollment in March 2009. Limitations: The challenges of this trial included a lack of information from subjects who did not enroll, increasing the difficulty of interpreting the feasibility phase. Conclusions: Successful recruitment to a randomized trial that compares significantly different treatment approaches poses a challenge. © The Author(s), 2009.