In the lymphadenopathy occurring in the acquired immunodeficiency syndrome (AIDS) and the AIDS related complex (ARC), consistent histologic patterns have been described with some variants thereof, such as angioimmunoblastic lymphadenopathy-like or Castleman disease-like. In four such patients we have observed two other types of nodal lesions. Three patients had lymph node biopsies showing the characteristic histologic and immunophenotypic features of histiocytic necrotizing lymphadenitis (Kikuchi's disease). These were two males, 26 and 35-year old, with bilateral axillary and cervical lymphadenopathy, respectively, and one female, 29-years old with peripheral and abdominal lymphadenopathy. One patient had proteinaceous lymphadenopathy. This was a 26-year old man with disseminated lymphadenopathy and a small monoclonal IgG/k peak in the serum. Whether these two processes are direct effects of the HIV virus on the immune system or due to intercurrent etiologic factors, has to be determined. These observations, however, indicate that the range of nodal lesions (that the pathologist may encounter) in AIDS/ARC is wider than previously reported.