Rotylenchulus macrodoratus completed its embryogenic development in about 16-19 days at 18-32 C. On olive seedlings the life-cycle from egg to egg was completed in 45-55 days. The first molt occurred in the egg while the other three were superimposed, with retention of successive larval cuticles. Only immature vermiform and swollen egg-laying females were found attached to olive roots. Eggs are laid in a gelatinous matrix on the root surface. The maximum number of eggs seen was 55. Males were not parasitic. Dianthus barbatus, Parietaria officinalis, and Eriobotrya japonica were found to be hosts of the parasite. Observed in all infested hosts was an uninucleate giant cell that expanded from the endodermis toward the center of the stele in primary roots, and from the secondary vascular tissue toward the periphery of the cortex in secondary roots.