No underwear - ever. If you need something warmer it goes over the top of the shorts (or in the case of leg warmers under the shorts but not in the brief area). Can leave very bad chafing in, ummm, delicate areas. I find chamois butter unnecessary with the new synthetic materials but that is personal preference. I will second the wash everytime comment. Too much sweat for the bacteria to resist. At very minimum rinse well and hang to dry.