Weed species and densities of weeds present on the wheat farms at the Hanang plains in northern Tanzania were surveyed just before wheat harvest in May, 1986. The dominant weed wasSetariaspp. mainly,Setaria verticillata(L.) Beauv., which occurred at an average density of 58 shoots/m2. Additional weed species which occurred at average densities of greater than 1 plant/m2wereAmaranthusspp., mainlyAmaranthus retroflexusL., andGalinsoga parvifloraCav. The density ofSetariaspp. was greatest on the farms where wheat had been grown for the longest periods of time (18 and 10 yr). The densities of the other weed species on the Hanang wheat farms were not influenced by the number of years (1–18 yr) that wheat has been grown in monoculture. Several weeds were identified that are resistant to 2,4‐D, which is currently used for broadleaf weed control, but there was no indication that these weeds were becoming a serious problem.