A morphometric study of intraepithelial (IE) lymphocytes per 100 epithelial cells, villous heights (VH), crypt depths (CrD), and epithelial cell heights (ECH) was made on jejunal specimens of 17 patients with cow's-milk allergy (CMA), 52 with celiac disease (CD), seven with congenital lactase deficiency (CLD), four with acrodermatitis enteropathica (AE), four with giardiasis, and four with dermatitis herpetiformis (DH). The aim of this study was to investigate how the morphometric parameters correlate with each other. All cases with CMA, CD, and DH had villous atrophy with hyperplasia of the crypts, both signs being more severe in cases with CD and DH than with CMA. IE lymphocyte infiltration was more intense in specimens of patients with CD and DH (mean 76.0), than those with CMA (mean 62.5). The ECH were equally reduced in patients with CD and CMA. In a follow-up specimen at 1 year and 10 months for CD patients and 11 months for CMA patients the inflammation was reduced, and the VH were increased but still differed from the controls. In CLD cases the morphology of the villi and crypts of the jejunum was quite normal, with no IE lymphocyte infiltration; ECH were reduced. Minor morphological changes were seen in the specimens of patients with AE and giardiasis. In the whole study group there was a significant linear correlation, either positive or negative, between all variables measured (IE lymphocytes, VH, CrD, and ECH).