A greenhouse experiment was conducted to examine the effect of initial population density (Pi) of Meloidogyne graminicola on rice cv. Masuli and nematode population development. Sterilised soil was inoculated with second stage juveniles (J2) of M. graminicola to give 0, 0.1, 0.2, 0.4, 1, 2, 5 and 10 J2/g soil. Plants were grown in sandy loam soil containing pots under free draining conditions to stimulate upland rice production. Plant height and tiller number were unaffected, but root length, panicle number, total panicle length, grain number and weight declined significantly with increasing nematode density. At the highest initial population density (Pi), grain yield was reduced by 97%, but even at a Pi of 0.1 J2/g soil a reduction of 31% occurred. The relationship between Pi and relative grain yield fitted to the Seinhorst model was Y = 0.1 + (0.9) (0.3^Pi). The J2 population in soil and roots, and root gall index did not differ significantly with inoculum levels. However, the egg density in root differed significantly (P < 0.001) at plant maturity. Pi of 5 J2/g soil had the highest J2 and egg density.