In vitro glycation of sera dried on water-resistant medium (Parafilm) and on paper were studied by measuring the change of glucose level, fructosamine:total protein ratio, glycated protein concentration and alteration of electrophoretic mobility of sera before and after drying. The results suggested the instability of glucose in dried sera was due to in vitro glycation which was influenced by surface properties of media on which the sera were deposited. A new method for rapid effective in vitro glycation of sera was also proposed.