Within JHN, all data from the routine daily care of affiliated general practices are collected. These include patient characteristics such as year of birth, gender, the four digits of the zip code; structured data such as diagnosis codes (ICPC), medication prescriptions (ATC) and results of examinations (physical examinations, laboratory tests); and the free text ("SOEP lines") from the record. 

These data can also be linked to other data sources, such as CBS, hospital registries or the Integral Cancer Center of the Netherlands (IKNL).