Studies of two distinct human T-cell systems have provided the exciting finding that T cells are able to recognize non-peptide antigens: gammadelta T cells have been shown to recognize isopentenyl pyrophosphate and related structures and human CD1 has been shown to present microbial lipids and lipoglycans such as mycolic acids and lipoarabinomannan to T cells. T-cell responses to these non-peptide antigens should provide a strategic target for immunologic intervention in infectious disease.