Depending on how dirty they are, you could either wash wash them or not.
I typically brush and wipe the soil away - if need be sometimes with a damp paper towel.
Washing would be fine - mushrooms don't absorb much water (at least not as much as they are thought to - Alton Brown I think explicitly tested that with button mushrooms I think).
I don't like washing, especially wild mushrooms because, um, what's the point? I heat inactivate the bugs and dammit I want to experience the terrior effects. Also you don't want to soak morels (though at this time of year that's not what you have).
What mushrooms do you have (just curious)?