At the Humanities Faculty of the Free University of Amsterdam intensive efforts are being made to integrate computer-assisted learning in the curriculum of modern language teaching. The courseware is written in VULCO, an authoring language developed in-house and specifically designed for non-scientific applications. The paper describes a design concept for vocabulary acquisition courseware. The concept is characterized as 'modular', 'integrated' and 'learner-controlled'. The course-ware consists of a number of independent modules such as texts, a lexical knowledge base and various types of exercises. The design is 'integrated' in the sense that vocabulary learning proceeds from an authentic text in which new items are marked; at any point in the learning process this text together with the associated lexical database can be accessed. Exercises are related to this text. The didactic rationale for this approach is to provide constant confrontation with original reading material. The courseware is 'learner-controlled' in the sense that the learner is not compelled to adhere to a prescribed learning path - although this may be imposed by the teacher if so desired. The paper also briefly reviews an experimental study with the system for students of Dutch as foreign language.