This paper reports the results of a Monte Carlo investigation of Type I errors in the single group repeated measures design where multiple measures are collected from each observational unit at each measurement occasion. The Type I error of three multivariate tests were examined. These were the doubly multivariate F test, the multivariate mixed model F test, and a recently proposed multivariate extension of Mauchly's sphericity test. The study examined the efficacy of using the latter test as preliminary test to evaluate the tenability of the multivariate sphericity assumption made by the multivariate mixed model F. The study also examined the impact of violations of the multivariate sphericity assumption upon the Type I error control of the multivariate mixed model F. The results indicate an analysis strategy for the researcher confronted with the task of analyzing data gathered using this research design. Example data sets are presented to illustrate three likely patterns of behavioral data. The data analysis strategy is discussed as it relates to each data set. (Author)