The Australian Second Language Proficiency Ratings Scale (ASPLR), a performance-based instrument, is described. The origins of and rationale behind the Scale are discussed. The construction and use of the Scale are detailed. It is hoped that the usefulness of the ASPLR extends beyond the "on-arrival" English as a second language program for which it was originally designed to other areas involving second language learning. The major contribution of the Scale is seen in the analysis it provides of the development of second language proficiency and in the performanced-based definitions of proficiency levels that permit the practical skills attained by learners to be precisely stated. (Author/JB)