Sources resolved by the Infrared Astronomical Satellite in any band (12, 25, 60, or 100 microns) but smaller than eight arcmin in angular extent are to be found in the Small Scale Structure Catalog, also known as the catalog of "small extended sources." The catalog gives the infrared characteristics of 16740 objects including, e.g., galaxies, planetary nebulae and compact H II regions. The catalog lists for each entry and in each band separately: a position accurate to about one arcminute (rms); a flux density accurate to 50% (rms) overall, and better at high signal to noise ratios; a rough indicative size if a point source is present at the same location; and a variety of warning and processing flags. If a detailed shape description, or a more accurate position, flux, or size are needed, these must be determined from the raw detector output. Incompleteness is a complex function of wavelength band, brightness, and location, so the absence of an entry in the SSS Catalog does not necessarily imply the lack of detectable extended emission. Many entries, mostly at 60 and 100 microns, refer only to emission features that are details in larger structures known as Galactic cirrus. Complete documentation, including a description of the catalog format, is contained in the printed version.