A research project is discussed involving the collection of production data from writing samples of 375 adult learners of English divided equally among five language backgrounds: Arabic, Chinese, Japanese, Persian, and Spanish. Information is presented about three constructions: (1) subject relative clause, (2) infinitival complement on verb, and (3) passive construction. For each structure, total production, total error production, and error types are analyzed. Three error type characteristics and two learning patterns are described. It is argued that neither the error type characteristics nor the learning patterns would have emerged if total production, total error production or error types had been considered in isolation. (Author/AMH)