Higher education has been impacted significantly by the proliferation of online instruction. Despite this trend, empirical investigations of this delivery method have lagged. Many have documented the need for research on online student characteristics, yet current literature consists of personal teaching experiences and anecdotal observations. To address these issues the authors conducted three studies. The goals were to describe how the new measure of online student characteristics (i.e., TOOLS--Test of Online Learning Success) was constructed and validated, outline the contributions the measure has made to our knowledge of online learners, and review the research literature that supports the findings. The results demonstrated the measure's simple and stable structure, construct validity, criterion validity, internal reliable, and test-retest reliability. The measure, administration guidelines, scoring procedures, and outcome interpretations are provided in the public domain. The different purposes for which the measure may be used are discussed. The paramount student characteristics that emerged are presented and discussed in regards to other research findings. (Contains 4 tables and 1 figure.)