The fact that some people learn a second language more easily than others has prompted numerous studies designed to link one factor or another with successful language learning. This work examines a large number of these studies to assess the importance of various factors involved in language learning. The influencing factors suggested are grouped into three categories: personal, situational, and linguistic factors. Considered first is the particular set of personal characteristics each individual brings to the task of learning a second language. These include general intelligence, language aptitude, attitude and motivation, psychological traits, age, socioeconomic status, and sex. The variety of learning situations is then discussed. Situational factors include the setting in which the language is learned and the amount and distribution of time devoted to it. In addition, if the language is learned formally, the method used and the characteristics of the teacher must be considered. Finally, linguistic factors are examined. These include both the differences between the first and second languages and the characteristics of the second language itself. (Author/AMH)