Hey everyone, when I use the scripts that : ........ filen='filename.HDF' sdsfileid = hdf_sd_start(filen,/read) hdf_sd_fileinfo,sdsfileid,numsds,ngatt print,numsds hdf_sd_fileinfo,sdsfileid,numsds,ngatt names = strarr(numsds) ndims = lonarr(numsds) dtype = strarr(numsds) for i = 0, numsds - 1 do begin sds_id = hdf_sd_select(sdsfileid, i) hdf_sd_getinfo, sds_id, name = na, ndim = nd,type= typ names( i ) = na ndims( i ) = nd dtype(i) = typ endfor ...... I get the 'numsds' is 6. But whe I use hdf_browser, there is 8 fileds. And I am sure that the number of fileds is 8. So how to the other two fileds? Thanks Mike