I am writing netCDF files with IDL 8.1 and am encountering a problem when I use the USHORT keyword in calls to the NCDF_VARDEF function. I get the following error message: NCDF_VARDEF: Unable to define variable. (NC_ERROR=-45) If I found the correct interpretation of error code -45, it means it's a bad data type. I don't get this message with other data types such as long integers, floats, bytes, or even signed 2-byte integers (using LONG, FLOAT, BYTE, and SHORT keywords, respectively). I just can't seem to write unsigned 2-byte integers using the USHORT keyword for some reason. Has anyone else encountered this? Am I missing something? Thanks!