A method for determining Avrami parameters directly from isothermal calorimetry data has been developed. Using the method, we have determined values of the time constant tau and exponent n. The tau values agree reasonably well with results from a previous, more cumbersome graphical method of analysis. There are greater discrepancies between the n values derived using the two techniques, presumably due to differences in the magnitudes of time increments by which the data fits are shifted in the two methods. The method is illustrated by analysis of isothermal calorimetry curves for precipitation in several aluminum alloy samples.