Ontologies are being used nowadays in many areas. Within the bioinformatics area there are a number of bio-ontologies that cover different aspects in molecular biology. Many of these ontologies contain overlapping information. In applications using multiple ontologies it is therefore of interest to be able to merge these ontologies. In this paper we describe a prototype implementation of an ontology merging tool for DAML+OIL ontologies. The tool generates suggestions for merging roles and concepts and for is-a relationships between concepts. We also evaluate the quality of the suggestions using well-known bio-ontologies