Purpose: Studies have demonstrated gender differences in the burden of cardiovascular outcomes for patients with dyslipidemia. Progress in identification of the sex/gender composition in Randomized Controlled Trials (RCTs) is crucial for understanding the distribution of therapeutics effectiveness in the population according to sex/gender. The purpose of this study was to investigate the evolving pattern of sex/gender disparity in participants of RCTs on statins between 1990 and 2010. A secondary objective was to evaluate changes in the pattern of the average age of participants of RCTs on statins between 1990 and 2010. Methods: This review focused on RCTs on statins that reported participants’ numbers by sex/gender. Studies were identified from an initial PubMed search using several combinations of MeSH terms. The search was limited to the RCTs on adults in English-language publications. The dates for search were set between January 1, 1990 and December 31, 2010. Results: In the 1990s, RCTs on statins with an average of more than 500 participants included 18.6% women [95% Confidence Interval (95% C.I.): 16.31%, 21.13%]. By the first decade of the 2000s, women comprised, on average, 31.45% [29.45%, 32.52% (95% C.I.)] of the total cohort of RCTs with more than 500 participants. Regression analysis illustrated a significant increase in the recruitment of women for RCTs of statins (p-value < 0.01). Furthermore, analysis of the average age of participants illustrated a significant trend (p-value = 0.03) towards an increase in the average age of the participants in RCTs on statin between 1990 and 2010: the average age of participants in the 1990s was 58 years [56, 60 (95% C.I.)] and in the 2000s it was 62 years [56, 60 (95% C.I.)]. Conclusion: This study demonstrates significant progress in the inclusion of women in RCTs on statins. This finding reflects the efforts of different agencies and groups to increase the representation of women in clinical trials.