This paper discusses and provides some preliminary data on errors in APL programming. Data were obtained by analyzing listings of 148 complete and partial APL sessions collected from student terminal rooms at the University of Alberta. Frequencies of errors for the various error messages are tabulated. The data, however, are limited because they provide no detailed information on how each error type was caused and do not include logic errors. The data indicate that assignment errors are the most common type; and that syntactic and semantic errors are about equally frequent. (VT)