This paper reports on Educational Testing Service research studies investigating the parameters critical to reliability and validity in both the direct and indirect writing ability assessment of higher education applicants. The studies involved: (1) formulating an operational definition of writing competence; (2) designing and pretesting writing assessment instruments; (3) identifying and controlling parameters influencing a writing assessment program; and (4) the scoring and interpretation of measurement outcomes. Data from 638 college applicants representing three foreign language groups plus a small sample of native English speakers were collected from four writing samples scored by several methods, Test of English as a Foreign Language (TOEFL) scores, and Graduate Record Examination (GRE) General test scores. Correlational and factor analyses revealed these key findings: (1) holistic scores, discourse-level scores, and sentence-level scores were so closely related that holistic scores alone should be sufficient; (2) correlations among topics were as high across topic types as within topic types; (3) similar scoring by different types of raters suggest substantial agreement in the standards used; (4) writing sample and TOEFL scores were highly related but each also measured other aspects of English proficiency; and (5) relationship patterns between holistic writing sample scores and item type scores within GRE General Test sections were consistent with other GRE studies. (Author/BS)