Residues of agricultural chemicals in soil and run-off water are a major cause for concern in cotton production. Microorganisms are known to be important in residue degradation but the role of soil fauna in this process has received much less attention. In some cotton-growing soils the Collembolan, Proisotoma minuta, is a predominant species and may contribute to residue reduction. The effect of herbicides used in cotton-producing areas on P. minuta is being examined to determine whether residues are likely to be metabolised by the insect.