The distribution of glutamate receptor subunits in human spinal cord has yet to be fully elucidated. The aim of this study was to examine the distribution of mRNAs for the subunits of the AMPA type of glutamate receptor (GluR A, B, C and D) in control human spinal cord using in situ hybridization and to examine in parallel the expression of these mRNAs in patients with sporadic amyotrophic lateral sclerosis (ALS). We also quantitated mRNA levels for these subunits in spinal cord homogenates. The relative abundances of the receptor subunits were as follows: GluR A > GluR B > GluR D > GluR C with A, B and D expressed in foci corresponding to the medial, lateral and ventral clusters of motor neurones. Quantitation of homogenates revealed a significant decrease (38%) in GluR A mRNA in ALS spinal cord compared with controls, and a 67% decrease of GluR B mRNA compared with controls. Levels of GluR C and D were too low to analyse densitometrically.