Weed control along railway lines is normally executed by mowing, herbicide spraying or a combination of the two. The growth retardant bispyribac-sodium inhibits the biosynthesis of amino acids in plants, and is lethal for some weed species. The author tried to control weed flora in addition to retarding growth using this chemical. After three years of treatment, large-size weeds such as tall goldenrod and mugwort were eliminated, with foxtail and southern crabgrass occupying the vacant spaces. These vegetation changes also brought a reduction in the total weed biomass. The results indicate that the growth retardant is suitable for long-term vegetation control along railway lines.