Cellulose and its derivatives (methyl cellulose, sodium carboxymethyl cellulose, hydroxymethyl cellulose and hydroxypropyl cellulose) used as excipients in pharmaceutical industry can be characterised by simultaneous thermoanalytical (DTA and TG) methods, based on the temperatures of exothermic peaks. Lignine cellulose can be identified by taking into account the difference in temperature between the first exothermic DTA peak and the corresponding DTG peak.