To be safe, I would get a hard scrub brush with some bleach & water. Wet the deck, apply bleach and SCRUB away. You can rent a pressure washer to remove the harder stains.
Gas pressure washers are the best, just make sure to use the "fan" setting or risk tearing holes in your deck.
Practice using the washer on a sheet of plywood to get the hang of it before using on a deck.
Rick

Thanks, but I've heard that pressure washers can damage the wood if you don't know what you're doing (and I haven't a clue).

And I would prefer to use something less toxic than bleach, if possible.

RESTORE A DECK
www.restore-a-deck.com

I've used and like the Dekswood from Flood.
Pressure-washing is great...BUT...
>>> Keep the pressure to 500 psi or less.
>>> Keep tip ONE FOOT away.
>>> Keep the tip moving.

Any higher than 500 psi, and you're crushing wood fibers...which is exactly what you DON'T want to do!!

If deck is 5 years old or more...sand it instead of "wet"-cleaning.

Check out Sikkens website too. Very good cleaning advice.

Faron

Here is a link that might be useful: Sikkens website

Sol-U-Mel wonderful cleaner, non-toxic. I have found that it works on just about anything!

dahdbs@comcast.net

You can try OxiClean, or CorteClean. A little harder to use but non-toxic and can be effective if you really stick to it.