In this study, we examined the validity of the measurement model and factor structure of Bass and Avolio's Multifactor Leadership Questionnaire (MLQ) (Form 5X). We hypothesized that evaluations of leadership?and hence the psychometric properties of leadership instruments?may be affected by the context in which leadership is observed and evaluated. Using largely homogenous business samples consisting of 2279 pooled male and 1089 pooled female raters who evaluated same-gender leaders, we found support for the nine-factor leadership model proposed by Bass and Avolio. The model was configurally and partially metrically invariant?suggesting that the same constructs were validly measured in the male and female groups. Mean differences were found between the male and female samples on four leadership factors (Study 1). Next, using factor-level data of 18 independently gathered samples (N=6525 raters) clustered into prototypically homogenous contexts, we tested the nine-factor model and found it was stable (i.e., fully invariant) within homogenous contexts (Study 2). The contextual factors comprised environmental risk, leader?follower gender, and leader hierarchical level. Implications for use of the MLQ and nine-factor model are discussed.