Traditional student evaluations of teaching do not adequately assess the essential constructivist-based practices that have been recommended for effective online instruction. There is a need for student evaluation of teaching instruments that are specifically designed to provide online instructors with valid feedback about the effectiveness of their online teaching practices. This study was undertaken to develop and validate a student evaluation of online teaching effectiveness instrument based on Chickering and Gamson's (1987) Seven Principles of Effective Teaching. Eight hundred and seven students enrolled in WebCT courses at a mid-sized university in the western United States completed the Student Evaluation of Online Effectiveness (SEOTE) for this study. Results from an exploratory factor of analysis of a randomly selected sub-sample of SEOTE responses of online students yielded four interpretable factors: Student-Faculty Interaction, Active Learning, Time on Task, and Cooperation Among Students. A confirmatory factor analysis of the second subsample found that the hypothesized four-factor model fit the data well. (Contains 3 tables and 1 figure.)