An organic grazing cattle herd in Tuscany (Italy) was monitored for parasites between 2002 and 2006. Every two to three months, faecal samples from cattle of different breeds and age were collected and examined for endoparasites, using both qualitative and quantitative parasitological techniques. Several environmental parameters were monitored and data on biodiversity and field margin biodiversity of grazing areas were also collected. All data were geo-referenced and plotted on a vectorial map using geographic information systems (GIS) software. Soil was classified as silt and clay/sand. The hydraulic drainage was poor and water pooling was observed frequently. The biodiversity of field margins was relatively high. Cattle were infected by coccidia, gastrointestinal nematodes, cestodes and trematodes. Prevalence and intensity of infestations were highly variable. In most cases, this variability was related to cattle breed, age, season and meteorological data. The Pisana breed was most commonly infected by Fasciola hepatica and Paramphistomidae. These infestations were associated with more frequent flooding and water pooling in the areas grazed by this breed.