Ontology learning is the application of automatic tools to extract ontology concepts and relationships from domain text. Whereas ontology learning tools have been fairly successful in extracting concept candidates, it has proven difficult to detect relationships with the same level of accuracy. This paper discusses the use of association rules to extract relationships in the project management domain. We evaluate the results and compare them to another method based on tf.idf scores and cosine similarities. The findings confirm the usefulness of association rules, but also expose some interesting differences between association rules and cosine similarity methods in ontology relationship learning.