First, apologies for the earlier post: I could have been clearer and thanks to JeffPN for pointing that out. Now to the crux of the issue: To remove any confusion at all about my position on rehydration, rehydrate unless you have a good reason not to. This is a simplification of the principle of pitching enough healthy yeast to complete the fermentation and to clean up the beer. It's not a simple question and yes, overpitching can be harmful to your beer. As a rule of thumb, a packet of dry yeast, sprinkled on top without rehydrating or a packet of liquid yeast will ferment five gallons of a 1.040 beer well. Your beer or your volume get bigger, you need more yeast. You can get more yeast, about double, by rehydrating the dry yeast in water before pitching because the stress of being pitched into wort kills off 40%-60% of the yeast. You may not want it. Hefeweizens should be underpitched to develop their flavor. If you like estery beer, you might want to underpitch. If you like diacetyl, Samuel Smith's comes to mind, you might want to underpitch. Key is to know why you are pitching the amount of yeast you're putting in. I like clean beers so I rehydrate, use multiple packets sometimes, do starters on a stir plate. Others like it differently. To all newbies: Follow the expert advice until you know why you should deviate from it. You'll make better beer that way both before and after you know what a deviation from standard procedures do. And discount 90% of what you read in the internet. The guy who made the best-ever barleywine by pitching a half a packet of dried yeast directly into the 95 degree wort likely got lucky. And by all means, anyone, myself included, tells you you have to do a thing a certain way, grab your wallet and run. I don't believe in dogma, you shouldn't either.