I've had the same problem with every pair of 991s and 992s that I've bought. They get old, they get wet, then they smell like urine. Despite what some of the older replies say, it's a problem with the shoes made by New Balance. It is NOT mold/mildew or such. It's a "chemical" in the deteriorating heel material that is smelling. Don't waste your time trying to clean them. Fortunately it is usually handled by NB as: "Bring 'em back and we'll replace 'em." And extra fortunate for me: I buy them at Nordstrom = easy return.