UPDATED7/11/07 Most soy sauce is prepared with wheat, thus making it off-limits to those of us who are gluten intolerant. The only exception I could discover is the San-J brand which can be found at natural food stores or ordered on-line from The Gluten Free Pantry. This same link will enable you to order gluten free soy sauce in single-serving packets.
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I also read the ingredients list on a bottle of LaChoy Soy Sauce. It contained the mandatory allergens list which listed soy as an allergen but not wheat. There were no sign of other gluten toxic ingredients. That sounds like good news to me but I have no documentary evidence so this is not an official recommendation. Also, I am not sure that this is true for all varieties of LaChoy sauce.
I found a recipe for a soy sauce substitute (8 parts molasses and 3 parts balsamic vinegar). Click here for more details. Let me know how it tastes.