This is a preliminary, draft outline for organizing information on the relation of climate to western forest diseases. The question is how to assess the threat of these diseases under a regime of climate change. Although forest diseases are often important, assessment of disease-climate relations is a challenging problem due to the multiple values at risk and the complexity of these systems. Several approaches are described and illustrated with examples for mistletoes and stem rust. Only a sampling of examples is given to illustrate a variety of concepts; many additional examples are to be found in the literature. Knowledge gaps are identified.