Secretory immunoglobulin A (sIgA) has been suggested to be a potential marker of stress in the human and the dog. We describe a simple method of saliva collection from rats for quantification of salivary sIgA in the first study of sIgA as a possible stress marker in the rat. Three groups of adult male rats were housed under different conditions (singly housed, paired with a female, and group housed). The animals were conditioned for the saliva collection by presenting a chocolate reward after every session and saliva was collected by soaking filter paper discs (5 mm in diameter) with saliva directly in the rats' oral cavity. The levels of salivary sIgA were determined by a novel paper disc rocket immunoelectrophoresis using sheep anti rat IgA antiserum. The resulting rockets had similar morphology as rockets in a standard rocket immunoelectrophoresis. Males housed singly showed stable sIgA levels with little variation while those housed singly with a female showed an initial decrease in sIgA followed by a steady increase. Males housed in a group (n = 6) showed a steady decline in sIgA levels. This indicates that sIgA levels are reduced by social stress and that this molecule may be a useful marker for well-being in the rat.