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It depends a bit on the scale - if you have a massive amount of affiliate links, they could get devalued, so some people have masked them in the past. The 302 does that, in a sense, but it also blocks the link-juice (or most of it). The 301 redirect would pass the link-juice, but there's a little more risk. If you're talking about 1000s of affiliate links and that's 90% of your link profile, I'd be careful. If it's just one part of your link-building strategy, it's probably not a big risk. As Istvan mentioned, the canonical tag is another option. Visitors would still see the affiliate URL (which may or may not be ideal, depending on your own business model), but search engines would pass link-juice to the target page. In that case, I'd make the canonical page match the landing page (the home-page might not be a good bet) - it's a bit situational. This post is a couple of years old, but it covers the basic options: http://www.seroundtable.com/archives/022446.html