I hv been using organic miso (in paste form) for 5 years, and it doesn't contain msg at all. Like what leng leng said, you hv to look at the ingredients. I hv to keep it in the fridge as it's fresh miso, not the powdered type. There are many types of miso in the market, so you hv to look at the ingredients.
If miso has msg, I would not recommend it and I don't like msg, cos it makes me thirsty.
The ingredients in the miso that I bought are: Organic soybeans, water, barley,sea salt and Aspergillus Oryzae(koji).