Although research shows that second language (L2) learners have major difficulties in developing their productive vocabulary skills, little research has been conducted on how to facilitate productive mastery of learned words. With this in mind, this study investigated the effects of task type and repetition frequency on improving receptive word knowledge to productive mastery. The 146 university students enrolled in an EFL course were assigned to four groups, each doing a different form of vocabulary exercises (multiple-choice, gap-filling, sentence translation and sentence writing) for 12 successive weeks. The 18 targets the participants knew receptively were divided into three sets that were repeated two, four and six times respectively. Productive knowledge of the targets was measured two weeks after the treatment. The results showed that (1) productive tasks contributed to significantly higher scores than receptive tasks regardless of repetition frequency, and some forms of productive tasks were more effective than others, and (2) repetition helped to promote the students' performance across tasks, but its effects started declining after the first several retrievals.