Thanks for the reply. I've been using the 18F4550 with a 20MHz resonator for a USB 2.0 application since 2005 and never had any issues. Are you saying the oscillator has to be 40MHz or the 18F4550 has to "think" it's running at 48MHz? My question wasn't due to any issues, I asked because I'm making a new design and the 48MHz and 20MHz oscillators are the same price and was curious if there are any benefits. In other words, would I see a difference using a 20MHz oscillator with /5 or using a 48MHz oscillator with /1?