Protocols were examined for the measurement of rates and enthalpies of polymerization (DeltaH(p)) using reaction calorimetry. DeltaH(p) was determined to be 70.2 kJ mol(-1) for a series of seeded styrene emulsion polymerizations under typical emulsion conditions, in good agreement with literature values. However, there was a significant deviation from this value for small-particle systems, which is ascribed to surface effects, i.e. environmental effects on DeltaH(p). Careful comparison between rate data obtained by calorimetry and by dilatometry leads to recommended procedures for obtaining reliable and accurate rate data using the former technique. (C) 2004 Elsevier Ltd. All rights reserved.