NSILA-S was localized by immunofluorescent antibody staining in the exocrine part of the pancreas and the submaxillary salivary gland of the rat, where part of the cells give positive reactions. To a lesser degree it was demonstrated in the kidney, where some – probably the actually functioning – nephrons give positive staining reactions within their tubular cells. Radioimmunoassayable NSILA-S was found in extracts of the pancreas (120–550 ng/g), of the submaxillary salivary gland (220–330 ng/g) and of the kidney (45 ng/g), whereas liver (and some other organs) contain practically no