What grains are gluten free?

Note that wheat is a type of grass, and is technically a grain.

Grains without gluten

Not all grains have gluten—only those closely related to wheat do. Grains which do not have gluten include:

• Corn (maize) and its variants or derivatives such as cornmeal, polenta, hominy, or masa

• Rice (all varieties)

  A note on rice: some varieties are called "glutinous". This just sounds similar to "gluten", but is in fact used to indicate the rice's stickiness. Glutinous rice does not have gluten, not even as traces, its stickiness comes from a special type of starch.

• Millet

• Sorghum
• Oats (although many oat products are processed in plants that may have had wheat)

Sometimes confused for grains

Note that the following gluten free seeds are not grains, although sometimes they are confused for grains:

• Wild rice
• Quinoa
• Buckwheat (despite the name, not a wheat nor a grain)
• Amaranth

Non-grains used as gluten-free starches and flours

Therefore, all grain-like, starchy, or flour-type foods which are not grasses are always gluten free, including wild rice, quinoa (despite any other issues), and so on.

Additionally, flours or seeds based on non-grain seeds, nuts, and legumes are always gluten free, although there may be other dietary sensitivities. These include:

• Almonds
• Soy beans
• Peanuts
• Chickpeas
• Mesquite flour
• Amaranth
• Quinoa
• Wild rice

Finally, starches and flours based on roots, rhizomes, and so on are gluten free, including:

• Potato
• Sweet potato
• (True) yams
• Tapioca

Grains containing gluten

The following grains are all wheat relatives, and have gluten to a greater or lesser degree:

• Wheat
• Spelt
• Rye
• Tritical
• Barley
• Kamut

Note that the following are all processed wheat products or specific wheat varieties, and should be avoided to maintain gluten free diets:

• Farina
• Durum
• Semolina
• Couscous

See also:

• Gluten Free Living
• WebMD guide to gluten free flours

SAJ14SAJ has great info. But in addition, if you are extremely sensitive to gluten as such with a severe allergy or certain digestive issues cross contamination is frequently an issue. Certain companies are more "allergy friendly" and have separate processing plants. Bob's Red Mill comes to mind for some of their products, but I've seen it with a few other companies as well. It has usually said something about it on the package, boasting about the separate processing plant.

It's usually trace amounts, but I have read quite a few posts from people with Celiac that have issues with the rice flour I pick up for cheap from most Asian specialty stores. So if you're just trying to avoid gluten as a general rule(as opposed to avoiding it because of allergy/illness) this will probably not matter much.