In the last few years a huge volume of material for genealogists has been published on CD-ROM. You can choose from hundreds of discs with everything from family histories, census indexes and passenger lists to clip art, maps and complete runs of rare genealogy journals going all the way back to the first issue. Books that take up several feet of shelf space require only a few inches in electronic form. Best of all, CD-ROMs usually cost only a fraction of what you'd have to pay for the same material in print.

But which to choose from this outpouring of shiny new genealogy resources? How can you tell which CD-ROMs are worth their weight in gold and which are better used as Frisbees or drink coasters? Try to answer several questions before you buy:

• What are the program requirements? Nearly all genealogy CDs run under Windows 95 or later, but some will also work with Windows 3.1 or a Macintosh.