Patient recruitment system, with at least one patient recruitment server, comprising at least one search routine that is configured to search for patient data records on the basis of recruitment characteristics, wherein the patient recruitment server comprises a notification routine that is configured to dispatch a recruitment notification concerning at least one patient data record found on the basis of the recruitment characteristics, wherein the notification routine is configured to automatically dispatch the recruitment notification concerning patient data records newly found on the basis of the recruitment characteristics, wherein the patient recruitment server is arranged outside of intranets of respective healthcare information systems of a healthcare institution, wherein the patient recruitment system comprises a plurality of distributedly located patient data processing units which, in at least one operation state, respectively receive patient data records from at least one healthcare information system, wherein the patient data processing units respectively comprise at least one pseudonymization routine, which is configured to pseudonymize patient data records received from healthcare information systems, wherein the searched patient data records are realized as pseudonymized patient data records, wherein the patient data processing units respectively comprise at least one depseudonymization routine, said depseudonymization routines being configured to determine at least one patient identification information that corresponds to a pseudonym information of the pseudonymized patient data records, wherein the patient recruitment server is located in a place different than the patient data processing units, wherein each of the patient data processing units is arranged in a local network and/or an intranet of the healthcare institution, wherein the patient data processing units and the patient recruitment server are connected by an encoded connection via the Internet, wherein technical precautions are provided, ensuring that neither patient data and patient data records which contain information regarding a patient who was at least examined in the healthcare institution or which comprise portions of electronic health records of one of the healthcare information systems nor the pseudonymized patient data records can leave the local network of the healthcare institution or the intranet of the healthcare institution, wherein the patient data processing units respectively comprise at least one pseudonym administration server which, in at least one operation state, stores the pseudonym information and the corresponding patient identification information, wherein, in at least one operation state, the pseudonym administration servers dispatch the pseudonymized patient data records, wherein, in at least one operation state, patient data processing servers of the patient data processing units receive the pseudonymized patient data records from the pseudonym administration servers, wherein the pseudonymized patient data records are stored in a database of the patient data processing server, and wherein the pseudonym administration server and the patient data processing units communicate only via the intranet of the respective healthcare information system.