In the area of large scale assessment, there is increasing interest in the measurement of students' written performance. At issue is whether the task demands in writing assessment can be simplified to involve the production of paragraph-length writing samples and/or multiple choice testing, rather than full-length essays. This study considers data generated by senior high school students in three response modes: written essay, written paragraph, and multiple choice items. The general issues of concern in this paper are the factorial equivalence of the scale scores derived in different response modes, and the comparative discriminant validity exhibited by the set of scores across response modes. The results suggest that repeated applications of the method of analytic scoring used in this study produce measures of the same underlying content; and that the factors reflecting the content of the five subscales (General Impression, Focus, Organization, Support, and Mechanics) are highly intercorrelated, and this interdependence is present no matter what response mode subjects are assessed in. (Author/BW)