The general theory on partially asymmetric (t−, t+)-EC/(d−, d+)-ED m-ary codes for the L1 distance is developed. In this metric, such codes are capable of correcting t− or less negative errors, detecting d− or less negative errors, correcting t+ or less positive errors, and simultaneously detecting d+ or less positive errors. Based on the elementary symmetric function, a wide class of these codes with efficient decoding algorithms are given. Let S(m, n, w, D) be the set of all the m-ary words of length n with real sum of their components being equal to w mod D. Any subset of S(m, n, w, D) is called m-ary constrained weight (CW) code of length n and is known to be a (D − 1)-UED code. Given a field, K, of prime characteristic p, some m-ary CW codes of length n ≤ |K| − 1 are defined. Such codes are (t−, t+)-EC/(d−, d+)-ED and have a redundancy of ρ(C) = n − log m |C| ≤ ρ(S(m, n, w, d + 1)) + t log m |K|, with t = min{t− + d+, d− + t+}, d = max{t− + d+, d− + t+} and w ∈ II N. In particular, for t ≤ p−1, a class of essentially linear and systematic (hence, easy to encode) m-ary (t−, t+)-EC/(d−, d+)-ED CW σ-codes with length n ≤ |K| + d/(m − 1) − 1, k ≤ |K| − t log m |K| − 1 information digits and n − k = t log m |K| + d/(m − 1) check digits are given. Also, some new hybrid partially asymmetric/unidirectional/symmetric error control codes are given and shown to be equivalent to the partially asymmetric (t−, t+)-EC/(d−, d+)-ED m-ary codes.