Determination of canine growth hormone (cGH) is of importance when evaluating the growth hormone status in dogs, for instance when diagnosing pituitary dwarfism and acromegaly. At present, analysis for the cGH content in canine blood has mainly been restricted to specialized laboratories which have had the capacity to develop suitable methods. We therefore formulated the objective of the present study to be the development of a generally accessible method utilizing commercially available reagents. We describe a radioimmunoassay (RIA) for the determination of cGH which was based on reagents developed for the determination of porcine growth hormone (pGH), thereby drawing benefit from the similarity between growth hormones from the two species. The RIA method was characterized by satisfying precision and accuracy parameters: intra- and inter-assay coefficients of variation (CV%) were 4-27% and 4-20%, respectively, depending on the cGH concentration of the samples. Recovery of added cGH and parallelism between standard curve and sample dilutions were acceptable, thus indicating identity between the calibrator system and the material under investigation (i.e. plasma samples). When measuring individual plasma samples or samples taken during clonidin response tests from normal dogs, dogs suffering from pituitary dwarfism and from dogs suffering from acromegaly, the results were comparable with previous findings.