This paper focuses on the design and evaluation of the computer-assisted vocabulary learning (CAVL) software WUFUN. It draws on the current research findings of vocabulary acquisition and CALL, aiming to help Chinese university students to improve their learning of English vocabulary, particularly that with which they experience most difficulty. It is argued that vocabulary should be learned explicitly as well as implicitly; learners need to be trained to become good learners, e.g., by being instructed in useful learning strategies, to enable them to learn vocabulary more efficiently and effectively. A design model of CALL efficacy is constructed to ensure the quality of vocabulary learning in CALL programs; it is employed in the design of the software WUFUN. Finally, the preliminary results of the software evaluation are reported and discussed. (Contains 4 figures, 11 tables, and 7 notes.)