This cross-sectional descriptive study of the Model of Domain Learning, which describes learners' progress from acclimation through competence to proficiency through the interplay of knowledge, interest and strategic processing/critical thinking (CT), examined its extension to maternity nursing. Based on the identified need for valid, reliable quantitative instruments measuring cognitive and affective aspects, three instruments were developed: a 20-item, polytomously-scored multiple choice questionnaire, a five item Interest Survey, and a written CT case scenario analysis. The sample was 87 baccalaureate student nurses in the third and final semesters. The instruments demonstrated mixed support for the Knowledge, Interest, and CT scales. Three principal component factors mapped well onto current definitions of CT. Further refinement of instruments and a broader sample were recommended. Appended is: Assigning a Score to an Open-Ended List of Priorities. (Contains 1 footnote, 4 figures, and 10 tables.) [funding provided in part by the University of Maryland's School of Teaching.]