Postpartum thyroiditis is a disorder which is morphologically similar to Hashimoto's thyroiditis, but differs clinically. The disorder presents with a transient period of thyrotoxicosis which may be so mild that it is clinically missed. Many of these patients subsequently develop hypothyroidism which also spontaneously resolves. Documentation that the hypothyroidism is transient would be necessary to establish the diagnosis. There is a proclivity for this disorder to develop in the postpartum period. Two patients are presented with this disorder, one with a transient hypermetabolic state and one with a transient hypothyroid state.