Assessment of student learning is a fundamental aspect of instruction. Special challenges and affordances exist in assessing student learning in online environments. This two-phase study investigated the types of assessment methods being used in online courses and the ways in which the online environment facilitates or constrains particular methods. In Phase One, syllabi from 24 online courses were reviewed in order to discover the types of method being used to assess student learning and contribute to the overall course grade. Five categories emerged: (1) written assignments; (2) online discussion; (3) fieldwork; (4) quizzes and exams; and (5) presentations. Phase Two consisted of a focus group and interviews with eight online instructors to discuss challenges and effective practices in online assessment. Challenges arose due to the impact of physical distance between the instructor and the students, adaptations resulting from the necessity of using technology for communicating with students, workload and time management issues, and the ongoing need to collect a variety of assessment data and provide feedback. Phase-Two interviewees offered strategies and suggestions to counteract the challenges they identified. The paper concludes with recommendations synthesizing the results of this study with those found in the literature. (Abstract by author)