Paratylenchus nanus populations were assessed by seasonal and monthly sampling of grazed pasture on silt loam soil in Waikato, New Zealand. The data were used to investigate P.nanus aggregation and relationships with abiotic factors, including soil temperature, rainfall, soil moisture and soil nutrients. P.nanus was more abundant at 10-20 than 0-10 cm soil depth and populations were greatest in summer. Aggregation declined from spring through to winter. P.nanus populations were positively correlated with soil temperature and negatively with soil moisture (seasonally) and rainfall (monthly). Monthly P. nanus abundance was also positively correlated with a combination of accumulated temperature and rainfall. On single occasions, soil phosphorus and nitrogen were significantly negatively correlated with P.nanus populations, and it is suggested that these associations were mediated through host plant abundance.