Experiments investigating resist heating were performed in a variable shaped electron lithography system. The temperature rise and associated change in resist sensitivity were related to the current density and size of flashes. The experiment avoids other contributing factors allowing the pure heating effect to be isolated. The response of the resist to temperature rise was determined by direct heating of the substrate using an exposure that causes no additional heating. The resist temperature rise under electron beam of variable size was also determined as a function of flash size and of throughput of lithography system. Applying multiple exposure with a delay between the successive shots, the time dependence on the heating effect was determined.