Three implants (tantalum pins 1.5 x 0.5 mm) were inserted in each lateral segment of the cleft maxilla of ten infants aged three to 33 months. To check the stability of the implants in the bone the distances between the three implants within each segment were measured by means of roentgen stereophotogrammetry (accuracy 0.05 mm) at intervals of 7, 35, 63, 147, and 287 days after initial examination and at varying intervals thereafter (maximal observation time 833 days). No implants were lost and 18 of 60 measured distances were stable (final changes less than 0.2 mm). The three implants were regarded as a rigid-body model which represented the segment in the calculations of motion. In all infants with complete clefts, transverse narrowing occurred immediately after primary closure of the lip, or primary palate repair, while subsequent movement followed individual patterns.