The aerobic metabolism of metaldehyde is suggested to occur via microbial and/or chemical degradation building mainly CO2 (74.3% AR after 365 days). Two minor metabolites, acetaldehyde and paraldehyde, were identified with accounts of ≤ %5 AR, whereas acetaldehyde reached its maximum level on day 273. The non-extractable residues increased during the incubation period from a mean of 0.5% AR to a mean of 17.1% AR. More than 98% of the 14C-activity observed in the potassium trap (74.4% AR) was indicated to be 14CO2. The 14C-activity observed in the ethylene glycol trap (11% AR) was identified for the most part as metaldehyde, furthermore higher molecular weight materials were found which could not be identified by GC/MS due to the insufficient mass. These observed nonidentified 14C-volatile degradates seem that volatilization from soil may afford a mechanism for loss of residues from soil.