The clinical-pathological characteristics of 11 patients with intestinal nodular lymphoid hyperplasia (INLH) are described. Five fulfilled the criteria for Herman's syndrome and presented all or several of the following alterations: dysgammaglobulinemia, recurrent respiratory tract infections, sinusitis, pneumonia and giardiasis; of the remaining six cases, in five gammaglobulin levels were not quantified and in one they were normal. All the patients in this group suffered from recurrent pharyngotonsillitis, and Giardia lamblia was isolated in four. In both groups the INLH occurred in young patients with an average age of 21 years. Eight of the 11 were men. The most frequent symptoms included diarrhea, steatorrhea and weight loss. Radiologically, INLH usually was a finding affecting the jejunum and/or the ileum. Prominent lymph nodes in mucosa and submucosa were documented histologically in all cases, and a large decrease or absence of plasma cells in the lamina propria was seen in 7 of the 11. In spite of the diversity in the treatment schemes instituted, symptoms persisted for months or years after diagnosis. In two cases (one with dysgammaglobulinemia and one without) associated intestinal lymphoma existed. Other associated diseases included non-deforming joint arthritis, erythema nodosum, and intestinal infection by E. coli and Entamoeba histolytica.