ABSTRACT. Carbohydrates were extracted from dormant, stimulated and germinated spores of Nosema algerae. Concentrations of total sugars were measured by the Anthrone test. Non-reducing sugars were quantified by NaOH hydrolysis followed by the Anthrone reaction, and reducing sugars by the Nelson's test. Glucose was measured by the o-toluidine test and a glucose oxidase assay. The concentrations of trehalose in the cytoplasm of the dormant, ungerminated spore was estimated to be in excess of 1.0 M. Trehalose decreased by 70% during the five-minute course of germination. All of the lost trehalose was converted to reducing sugar of which 70–78% was glucose. The osmotic potential increase caused by catabolism of trehalose appears to be sufficient for germination.