Hi there I'm having trouble opening a dataset in IDL5.6 and IDL6.0. IDL recognizes the file as HDF5 (H5F_IS_HDF5), successfully opens the file (H5F_OPEN), and even gives me the correct information about the datasets in the root group (H5G_GET_NMEMBERS, H5G_GET_MEMBER_NAME). However, opening a dataset in this file (H5D_OPEN) fails, with this error message: % H5D_OPEN: dataset not found: (67108864, "Density") I suspect the problem is due to incompatible versions of HDF5. IDL's library (idl_hdf5.so) uses HDF5 v.1.4.3, whereas I used the newer version 1.6.0 to create the file. Has anyone experienced a similar problem? Found a solution (short of reverting to call_external wrapper functions)? Would any RSI rep. care to comment on the possibility of a version of idl_hdf5.so based on HDF5 v1.6? Thanks, mike