To convert the BIL format files in ArcView, simply add them to a view as an image data source (you can select that option in the lower-left corner of the Add Theme dialog box).

Then you can create a GRID that ArcView can use and display by choosing ‘Convert to Grid’ under the theme menu. For this option to be available, the image theme will have to be the active theme and the Spatial Analyst extension will have to be turned on.

However, there seems to be a bug in ArcView, that prevents the correct display of some grids in a view or a layout according to the legend. The bug affects grids with a pixel or attribute value range greater than 1-1,000,000 for floating point grids and 1-100,000 for integer grids. The grid values are referenced correctly, but the default screen color values don�t match the GRID legend. A workaround is to recode the GRID into fewer, strategically grouped attribute classes.
For ArcInfo:

At the arc:>, use the following “IMAGEGRID” command to convert BIL files.

IMAGEGRID <input .BIL file> <output GRID data>. Use defaults for the out_colormap_file, in_band and Interpolation method.