(1) Veronica filiformis established, spread and survived both on bare soil and in a grass sward. Its spread was aided by fragmentation and the subsequent rooting and establishment of daughter plants. The plants were little damaged by mowing. (2) The rate of increase of V. filiformis was greatest under cool, moist conditions. (3) Two annual species (V. agrestis and V. persica) survived for one season on bare soil and produced large numbers of seedlings-few of which survived the next year. Neither species survived for more than one season in a grass sward; although seed was produced no seedlings established successfully. (4) Veronica filiformis is a very successful perennial weed in short turf and its present rapid rate of spread in some areas is likely to cause substantial increases in the cost of control measures.