The work presented in this thesis documents studies on the impact of RNA interference (RNAi) on potential control target genes and how this alters the phenotype of the pre-parasitic stage of the plant parasitic nematodes (PPN), Globodera pallida and Meloidogyne incognita. A wide range of targets were selected across all the main tissue types within the worms (hypodermis, muscle, nervous system, subventral gland, dorsal gland) and significant knockdown was achieved (using short-interfering [si]RNAs) in all tissue types except the dorsal gland. Overall, the data strongly support the utility of PPN J2s as a model for functional genomics studies using RNAi. Further work was carried out on selected targets including the neuropeptide-encoding genes, Gp-flp-30 and Gp-flp-31 which are thought to be only expressed in PPN species. These targets showed reduced target transcript levels following RNAi, however not to the same degree as most of the previously targeted genes; their silencing did not induce a significant phenotype suggesting they are involved in functions other than normallocomotion/chemotaxis. We also targeted Gp-flp-21 and its putative receptor encoding gene Gp-flp-21 R which in Caenorhabditis elegans modulate sociality. Silencing either gene did not alter PPN motility but did disrupt positive chemotaxis, consistent with a role in chemosensation and consistent with the FLP-21 R being the FLP-21 receptor. Finally, the work reported here has shown that silencing Gp-ace-2, which encodes an acetylcholinesterase, results in complete paralysis of the parasites and prevents them from infecting their host plant and thus complete their life cycle. These data provide functional validation for a variety of PPN control targets.