A methodology has been developed to enable a single, gaseous sample to be collected from the diluted exhaust stream of heavy duty diesel engines operating over the European 13 mode ECE R49 emission cycle. The sample consists of timed contributions of dilute exhaust gas from each mode (weighted appropriately) to provide a gas sample that is representative of the complete cycle. The sample is collected in a Tedlar bag prior to GC analysis for individual hydrocarbon speciation. This methodology has also been extended to allow for the collection of a representative carbonyl sample using 2,4-dinitrophenyl-hydrazine (2,4-DNPH) impregnated cartridges. Results obtained from these systems are reported and compared to results obtained from light duty (diesel and gasoline) investigations.