Summary. In vitro-propagated banana plants cv. Goldfinger were not resistant to Radopholus similis unless they were at least 28 weeks old at inoculation. By contrast, a Pisang jari buaya clone and SH-3142 expressed resistance when inoculated from 12 and 8 weeks of age respectively. Fewer nematodes were recovered from older plants of Goldfinger than from Cavendish 3 weeks after inoculation (i.e. before a life cycle could be completed). This suggests that the resistance mechanism of Goldfinger involves reduction in both penetration and reproduction by nematodes. Comparison of recovery of nematodes following inoculation of plants at different ages showed that resistance assays should use plants which are at least 28 weeks old. Also, plants should be at least 28 weeks old when establishing a plantation to reduce the chance of severe damage by high nematode densities. Goldfinger was more tolerant to R. similis than was Cavendish when supporting the same number of nematodes.