The pesticide phosphine (PH(3)) is a suspected carcinogen and a known clastogen which has been shown to produce chromosome damage in agricultural workers. To confirm and extend these results we evaluated 22 phosphine appliers and 26 controls matched for age and smoking status. Two independent methods were used to evaluate exposure: fluorescence in situ hybridization (FISH) with whole-chromosome paints of chromosomes 1, 2, and 4 labeled in a single color to quantify translocations in peripheral lymphocytes, and the glycophorin A (GPA) assay to quantify phenotypically mutant (NØ or NN) erythrocytes. No differences in the frequency of translocations were found in the phosphine appliers compared to the controls, and no effect of cigarette smoking was observed. However, a significant increase in the frequency of translocations with age (P<0.0001) was seen. No effect of phosphine exposure or cigarette smoking was observed in the GPA assay. These results are in contrast to previous findings from this same population which showed an increase in chromosome aberrations among phosphine appliers. The results are most easily interpreted as supporting the effectiveness of the personal protective equipment that is now worn by the workers but which was not employed prior to and during the earlier studies.