Introduction: Healthcare Information Systems (HIS) are in most cases complex systems that store and manage large amounts of medical data. When such a HIS is intended to be used in medical research, it presents the system designer with a double challenge: the need for complexity and flexibility at the same time. In this paper we present a database design pattern along with a Graphical User Interface (GUI) design that empowers the researcher to build metadata structures, which are supported by relational data structures on a database server. Method: As most of the data gathered during a medical research is viewed as having a hierarchical structure, we based our approach on modeling trees and multitrees. The system that we have developed is based on database design patterns and GUI prototypes. Issues regarding data structuring, data entry and data retrieval are addressed. Results and evaluation: The structure and functionality of the proposed system are presented, with emphasis on three major fnctions: data structuring, data entry and data retrieval. Some considerations regarding the implementation of the system are also included in this chapter. Conclusions: By using the presented approach, medical researchers can quickly and efficiently configure a customizable software system for recording their data in more complex structures than tables or spreadsheets, while benefiting of the consistency of a relational database.