The effect of N-linked glycosylation on secretion, activity, and stability of alpha-amylase from Aspergillus oryzae grown as dispersed filaments was studied. In the presence of tunicamycin the fungus grew either as dispersed filaments or as one large pellet, whereas growth was as dispersed filaments in all control cultures. The presence of tunicamycin affected neither biomass, level of secreted alpha-amylase, nor total amount of secreted protein in cultures growing as dispersed filaments. In these cultures both glycosylated and nonglycosylated alpha-amylase appeared in the culture medium as well as in the cells, whereas in control cultures only the glycosylated form of alpha-amylase was found in the medium and in the cells. The presence of nonglycosylated alpha-amylase in the medium seemed to result from active secretion rather than from autolysis of the mycelium or extracellular deglycosylation. Deglycosylation with Endo H of crude alpha-amylase in culture filtrate did not affect its stability towards heat, acid pH, or proteolytic degradation.