This study investigated the validity of various approaches to the measurement of English composition skills. Over 600 11th and 12th-grade students were asked to write five 20-minute essays on different topics, to take six objective tests of writing ability, and to do two interlinear exercises. Twenty-five experienced readers assigned scores of three, two, or one to each essay. The total of the 25 scores per essay became the criterion for evaluating the validity of the objective tests and interlinear exercises. The sums of 20 ratings on four of the essay topics became the criterion for evaluating the fifth topic as a predictor. Later, a larger number of readers regarded the essays on two of the topics to assess the effects of reading under field conditions. Findings indicated that (1) the reliability of essay scores is primarily a function of the number of different essays and the number of different readings, (2) objective questions designed to measure writing skills prove to be highly valid when evaluated against a reliable criterion, and (3) the most efficient predictor of a reliable direct measure of writing ability is one which includes essay questions or interlinear exercises combined with objective questions. (Tables presenting data from the study are included.) (JS)