How do I replace the cabin air filter on my 99 Lexus ES300

It's a little harder to find and harder to replace than slightly newer ES models.Remove driver's floor mat. Kneel at the driver's door aperture, pull back the carpet at the accelerator pedal towards the stereo/center console you will see a white plastic square gridded panel about 5 inches square, pry that off its three clawed grips that secure the panel and the air filter can then be slid outward.

you can look this article, http://chinasinoy.com/service/how-to-change-cabin-air-filter-95.html