Abstract: The IDL program "hdfeos2bin.pro," written by Terry Haran of the National Snow and Ice Data Center, extracts data arrays from an HDF-EOS file and writes the arrays to separate flat binary data files. Currently, this program has been tested with Moderate-Resolution Imaging Spectroradiometer (MODIS) sea ice and snow cover products at NSIDC; however, it is designed to work with any HDF-EOS file. ... The program "hdfeos2bin.pro" calls several subprograms that read swath or grid input data from HDF-EOS files and writes the output data to flat binary files. While this program has limited capabilities, it effectively demonstrates the use of HDF-EOS library calls without the need for installing and linking to HDF and HDF-EOS libraries, because IDL effectively provides these libraries as built-in functions and procedures. The "hdfeos2bin.pro" program contains detailed documentation within the code.