In a mass screening project, 872 neonates were examined clinically and by ultrasound. Hip joint stability was assessed in the ultrasound stress test showing a normal or physiologic instability, in the range of 0 to 2 mm. Along with the dynamic examination, a modified Graf's method was used. All obtained sonograms were submitted to careful assessment by one of authors, including regular measurement of alpha and beta angles. This relatively small group in the low-risk population served as a model of normality. White newborns compared with an black Caribbean group did not show the presence of apparent primary acetabular dysplasia. Both methods--dynamic ultrasound test and Graf's scanning--seemed to us to be valuable.