The measurement of organically bound tritium in environmental samples is essential for assessing the impact of tritium releases in terms of doses to the general public and a growing number of laboratories are now required to make them. Interlaboratory comparisons provide one way for laboratories to practice and check their analytical methods and procedures. At AECL's Chalk River Laboratories, two organic matrices with tritium concentrations less than 1.5 kBq/g were developed and distributed to seven laboratories in Canada, Europe and Russia for measurement. Some participants experienced difficulties in analysing the samples, especially with the lower concentrations, where results varied by more than an order of magnitude. Laboratories incorporating procedures such as rinsing to remove tritium from exchangeable sites, using standardized combustion methods and purifying the combustion water obtained more reliable, consistent results. The preparation of the standard reference material must be carefully executed in order to produce a homogeneous sample of uniform size. The tritium measurement community would benefit if standard reference materials in the environmental concentration range were available.