A new size exclusion chromatography column packed with 1.7μm particles and possessing 200Å pore size has been critically evaluated for the determination of proteins and monoclonal antibody aggregates.In a first instance, the kinetic performance of this column was compared with that of a conventional column packed with 5μm particles and with a recently launched 3μm material, also possessing 200Å pore size.In average, 2–5 times lower plate height were achieved on the 1.7μm packing, compared with the conventional 5μm particles. It was also demonstrated that elevated mobile phase temperature (up to 50 or 60°C) allows improving the kinetic efficiency by 20-40% in size exclusion chromatography, compared to 30°C. On the other hand, the new 3μm material performed only slightly lower kinetic efficiency than the 1.7μm one. When considering the upper pressure and temperature limits of these three columns, the 1.7μm column systematically outperforms the 5 and 3μm materials in the “practical” plate number range (N<30,000) and analysis times could be cut by 2–4 times. The column packed with 5μm particles was only beneficial for plate counts beyond 100,000 plates, while the 3μm packing could be considered as a good compromise between speed, efficiency and pressure.Besides the excellent kinetic performance of 1.7μm size exclusion material under high temperature conditions, some artifacts were observed when quantifying protein aggregates. Indeed, both high pressure observed with 1.7μm particles (shear forces, frictional heating) and elevated temperature produce some non negligible amount of on-column additional protein aggregates.