Large horizontal Douglas fir timbers with interior decay fungi were used to evaluate the effectiveness of Vapam (sodium N-methyl dithiocarbamate) and chloropicrin in controlling decay fungi. Fumigants were applied in holes drilled in the timbers or flooded into checks. The efficacy of the fumigants in arresting interior infection was evaluated by comparison of the fungal population after fumigation for a 16-month period to that prior to fumigation. Both chloropicrin and Vapam controlled the growth of decay fungi in the interior of Douglas fir timbers. Neither fumigant was as effective in controlling molds as in controlling decay fungi. See also AATA 15-418.