The recent novel temperature-modulated DSC (MDSC(TM) TA Instruments) technique has been applied to the measurement of the thermal properties of chalcogenide glasses of the (As0.33S0.67)(100-x)Y-x (where Y is Te or I) system in the glass transition region in bulk glasses and its thin films. All samples in this work were given the same thermal history by heating to a temperature above the glass transition, equilibrating and then cooling. The reversing and nonreversing heat flows through the glass transformation region during both heating and cooling schedules were measured and the values of the parameters T-g, Delta H, C-p and Delta C-p, which characterize the thermal events in the glass transition region, were determined. The structurally determined parameters T-g, Delta H, C-p and Delta C-p reveal a decrease with x because in the (As0.33S0.67)(100-x)Y-x glasses the average coordination number [r] decreases with increasing x from 0 to 10 at.% Y. No such thermal analysis has been done previously on (As0.33S0.67)(100-x)Y-x glasses. We discuss the results in terms of recent structural models for chalcogenide glasses.