Soil was sampled in 1973 from 32 plots of a pasture of ryegrass, cocksfoot, and white clover that had been sown in autumn 1967. The trial had a factorial layout. Treatments were grazing by 14.8 or 22.2 ewes per ha, and topdressing with 125 or 500 kg superphosnhatc/ha annually and with 0 or 5.50 tonne lime/ha in 1968. Populations of Pratylenchus, Paratylenchus, Heterodera triiolii larvae, Mononchidae, and total nematodes changed significantly in response to at least one of the treatments; no change was found in Helicotylenchus, H. trijolii cysts, or Dorylaimida. The most marked effect was a fourfold increase in the Pratylenchus population in response to both liming and superphosphate. Stepwise multiple regression of nematode populations with dry matter production and five soil chemical factors gave only eight significant coefficients, three with soil P, four with soil pH, and one with soil Ca. Increase in Pratylenchus in the heavily fertilised plots may have been partly responsible for the low increase (3%) in dry matter production. The role of nematodes such as Heterodera, Pratylenchus. Paratylenchus. and Helicotylenchus, which are widespread in New Zealand pastures, is worth further investigation.