No, although you should sterilize them before using them for the first time (the same goes for pacifiers, sippy cups, or other feeding gear). After that, many pediatricians feel that dishwashers (especially those with hot, sanitizing rinse cycles) or a good scrubbing with hot soapy water will do a thorough job of getting the bottles and nipples clean and free of germs. Just be sure to place bottles in the top rack of the dishwasher so they don't melt. Use a basket for small parts like the nipples. It's not a bad idea to sterilize your supply of bottles once in a while, just to be on the safe side, and especially after your baby's been sick. Some parents buy a special bottle sterilizer, but they're not necessary. Soaking bottles in a big pot of clean, boiling water for about five minutes works just as well.