The influence of variables on the observation of thermal events and on the determination of heats of transformation at freezing and thawing in aqueous solutions was investigated using modulated temperature differential scanning calorimetry (MTDSC, ODSC). The investigated systems were pure water and dilute aqueous solutions of polyethylene glycol (PEG) 6000, The influence of eleven combinations of frequency, amplitude and underlying heating rate was analyzed in heating-cooling scans. The selection of variables had a great impact on the shape of the c(p) component curve as well as on the amount of heat expressed by the c(p) component, Delta H-c, of the thermal event. The conventional Delta H-values were not influenced to the same extent. The ratio Delta H-c/Delta H of the melting process might be an expression of the degree of relative crystallinity in frozen aqueous solutions. The requirement of operational setting is an appropriate degree of oscillation in combination with a number of modulations over a distinct transformation temperature. The selection of variables must produce a heating-cooling scan.