Studies of post-mortem interval on the stability of RNA from a number of various mammals have shown RNA to be stable for between 24 and 48 h following death. As yet there have been no studies looking at RNA stability in post-mortem tissues of poikilothermic fish. Brain, kidney, liver and muscle were collected from Atlantic salmon (Salmo salar) parr and samples of each tissue were placed into RNAlatertrade mark after 0-24 h post-mortem storage at room temperature. Electrophoretic analysis of the total RNA showed degradation of ribosomal RNA only in muscle from 8 h onwards. Probing of northern blots with beta-actin showed that, in the brain, beta-actin mRNA was stable for 24 h post-mortem but degradation of mRNA was observed after 8 h with the kidney and liver and after 4 h with the muscle. Expression of the weakly expressed thyroid hormone receptor beta (TRbeta) was detected by reverse transcriptase polymerase chain reaction (RT-PCR) in all tissues up to 24 h post-mortem although a reduction in PCR product was observed after 8 h with muscle and 24 h with kidney. Analysis with an Agilent 2100 Bioanalyzer showed that the RNA integrity number (RIN) of brain total RNA remained constant for 8 h post-mortem with only a small fall at 24 h post-mortem. The RINs of the remaining tissues indicated degradation at 8 h post-mortem with kidney and muscle and at 24 hours post-mortem with liver. Taken together these findings show that degradation of Atlantic salmon RNA is tissue dependent but stable for at least one hour post-mortem.