Field investigations were carried out during 1987 and 1988 to compare cultural and chemical control of broad leaf and grass weeds present in the first and second harvest of Japanese mint. Unrestricted weed growth significantly reduced mint oil yield by 58% and 73%, respectively in the first and second harvests. Preemergence applications of terbacil (1.5 kg a.i./ha), pendimethalin (1.0 kg a.i./ha) or oxyfluorfen (0.25 kg a.i./ha) followed by application of fluazifopbutyl (0.25 kg a.i./ha) after first harvest were found to be highly effective in reducing weed density and dry weight and gave oil yield comparable to weed-free check. Applications of diuron (0.75 kg a.i./ha) or oxadiazon (0.25–0.50 kg a.i./ha) were less effective in weed control. None of the herbicides impaired the quality of Japanese mint oil measured in terms of menthol content. Successive weeding, hoeing and mulching (wheat straw 5 t/ha) also gave an oil yield equivalent to that of the weed-free control.