Some earlier SLA research suggests that zero pronouns should be easily acquired by second language learners, yet this has not been carefully examined because studies of nominal reference are usually limited to the acquisition of languages that do not have zero pronouns. This study examines how speakers of languages with zero pronouns (Japanese) and without them (English) use zero pronouns when acquiring a language that has them (Mandarin Chinese). The findings show that second language learners do not use zero pronouns as often as native speakers and that their use increases with proficiency. When examined more closely, it can be seen that the speakers have no difficulty using zero pronouns when there is a syntactic or semantic restriction, but they do have difficulty at the discourse level. It is claimed that this underuse of zero pronouns corresponds with other research that shows that second language learners tend to avoid pronouns in favor of full noun phrases. Some explanations for these phenomena are postulated.Much attention has been given to acquisition of nominal reference in second language acquisition for reasons best expressed by Chaudron and Parker (1990) in their study on the acquisition of English noun phrases:This paper was written from part of my dissertation under the guidance of Roger Andersen. His direction throughout the project was extremely helpful. I also thank Susan Gass, H. Gary Cook, and three anonymous SSLA reviewers for their useful comments.• 1995 Cambridge University Press 0272-2631/95 $7.50 + .10 353