A conference was held at the Seattle Research Center of the Battelle Memorial Institute during the summer of 1968. The object of this conference was to bring together research workers in the fields of category theory and homology theory and those who applied the results of these theories to their own mathematical disciplines within algebra or topology. Thus this was not, and was not intended to be, a tightly specialized conference in categorical algebra (by comparison with the Midwest Seminars), the expectation of its organizers being that the roles of category theory and homology theory within mathematics would emerge the more clearly from the conference and that the interplays of these theories with other parts of mathematics would be highlighted.