This paper studies impact of well edge proximity effect on circuit delay, based on model parameters extracted from test structures in an industrial 65 nm wafer process. Experimental results show that up to 10% of delay increase arises by the well edge proximity effect in the 65 nm technology, and it depends on interconnect length. Furthermore, due to asymmetric increase in pMOS and nMOS threshold voltages, delay may decrease in spite of the threshold voltage increase. From these results, we conclude that considering WPE is indispensable to cell characterization in the 65 nm technology.