Soil samples taken from the ridge of field-grown potato (cv. British Queen) as well as from bulk soil of the same field were incubated with sterile potato root leachate or water. Samples were filtered and filtrates used in an in vitro bioassay to determine their effect on hatch of potato cyst nematodes (PCN) Globodera rostochiensis and G. pallida. Concurrently an experiment was established where the sterile potato root leachate or water was incubated with a sterile soil wash. Ridge soil was shown to induce significantly more hatching than bulk soil, indicating the presence of PCN hatching factors. When a soil wash of ridge soil was used, this did not increase hatch, suggesting a role for soil microorganisms in the hatching process. Greater hatch of G. rostochiensis in bulk soil compared to G. pallida, suggests a role for soil microorganisms in spontaneous hatch of PCN in vivo.