Scientific evidence of both constructive and destructive movements of teeth has influenced the design and selection of attachments for overdentures. Dowel designs that would be acceptable for normal copings must be reconsidered in view of the mechanical effectiveness of parallel-walled dowels and screws. Coping designs for attachment overdentures must provide retention, resistance to rotation, and bulk when joined with the dowel and attachment, without negating the advantage of the reduced crown-root ratio. Splinting with a bar-type attachment (1) has advantages over splinting with a stud-type attachment that outweigh the disadvantages of bulk and (2) provides ease of replacement when one of several remaining teeth is excessively mobile. Part II will consider the various types of bar, stud, and auxillary attachments for the overdenture.