Compositions written by 48 university students of English as a Second Language (ESL) were examined as a step in the development of an index for proficiency in a second language. A feature analysis of the compositions revealed the following tendencies: (1) syntactic sophistication and tense usage improved as proficiency increased, (2) errors in morphology decreased between the "fair" and "excellent" levels, (3) prepositions were a consistent problem throughout all five levels, and (4) the number of errors in articles first increased and then decreased as the quality of the compositions improved. An analysis based on the relationship between features and length of composition produced the following results: average number of words per composition increased with proficiency, and the variance in number of words per sentence from one level to another, while striking, did not show a clear trend across levels of proficiency. Finally, the average number of error-free sentences increased significantly as proficiency level increased. (JB)