Portions of wieners and soybean foods (tofu and tempeh) remaining from inoculated pack studies using Clostridium botulinum spores were extracted with buffers which differed in having or not having 2 M urea. More samples had botulinum toxin when tested with extracts made in urea-buffer. Based on the LD50 of toxin extracted from wieners, urea-buffer extracted 30 to 100% more toxin than normal buffer.