The purposes of the study were: (a) to test for the factorial validity of the Maslach Burnout Inventory (MBI) separately for elementary (N = 1159), intermediate (N = 388) and secondary (N = 1384) teachers; (b) given findings of inadequate model fit, to propose and test an alternative factorial structure; (c) to cross-validate this structure across an independent sample for each teacher group; and (d) to test for the equivalence of item measurements and theoretical structure across these three teaching panels. Although confirmatory and exploratory factor analytic findings supported a three-factor structure, the deletion of two items (nos 12 and 16) yielded a better fitting model that was, for the most part, psychometrically and structurally invariant across groups. This study is the most rigorous to date in testing the factorial validity of the MBI in general, and as it bears on members of the teaching profession in particular.