Clinical, pathological and biochemical findings in the mannosidoses are described. Family studies showed granulocyte-rich white cell fractions to be the tissue of choice for carrier detection in beta-mannosidosis. Metabolic labelling studies using [3H] mannose demonstrated accumulation of Man beta 1-4GlcNAc in cultured skin fibroblasts from a patient with this condition. Alternative methods of egress from lysosomes were suggested for this compound by its secretion into culture medium and apparent reduction of storage with time in cultures. beta-mannosidase deficient goats are not thought to be a true animal model of the human condition, as although they showed a similar enzyme deficiency, the clinical presentation is much more severe and the major storage material (Man beta 1-4GlcNAc beta 1-4GlcNAc) is different.