The occurrence and distribution of organotin compounds (OTC) in effluents from two different landfills were investigated through the combination of three different analytical methodologies. In this way, the determination of the volatile OTC in biogases, the dissolved volatile and dissolved ionic organotin species in leachates was carried out using these complementary approaches. In leachates, up to nine OTC (i.e. methyltin, ethyltin, butyltin and mixed methyl-ethyltins) were detected at concentrations ranging from 0.01 to 6.5 ?g (Sn) L-1, which represents 1-38% of the total tin concentration. In biogases, five volatile tin species (i.e. methyltin, mixed methyl-ethyltin and ethyltin) were determined at significant concentrations reaching up to 25 ?g (Sn) m-3. The occurrence of the overall identified species is explained by both organotin-containing waste and endogenous alkylation pathways. Two parameters seem to significantly influence the effluent OTC composition: first, wet depositions both induce leachate dilution and alter methylation/ethylation mechanisms; second, evolution of the waste degradation stage yields different volatilisation mechanisms (i.e. permethylation or perethylation). The results obtained in this work outline the diversity and variability of the organotin contamination routes provided by multiple pathways. These phenomena can lead to the release of biologically harmful species in the environment if no efficient effluent treatment is applied. © 2007 Elsevier Ltd. All rights reserved.