Collagenous Sprue is a distinctive lesion of the intestinal mucosa associated with progressive malabsorption. The intestinal pathology is initially identified with the characteristic flat lesion of untreated Celiac Sprue. Thereafter, bands of eosinophilic hyaline material within the lamina propria become increasingly apparent. As the disease progresses, the mucosa becomes progressively thinner. Therapy, including the gluten-free diet, does not help. Some cases currently designated refractory or unclassified Sprue many prove to be Collagenous Sprue.