Published Article / The objective of this study was to examine the relationship between external markers typically used in external motion capturing devices and the true vertebral kinematics in the cervical spine. Twenty one healthy subjects were subjected to low dosage X-rays in five different positions, while radio opaque markers were attached to the skin at each vertebral level. Distance and angle parameters were constructed for vertebral prediction from skin surface markers. The causes of variation in these parameters were identified by investigating the correlations of these parameters with anthropometrical variables. Strong correlations of the parameters were observed in flexion, but in extension, especially full extension, the correlations were poor to insignificant. In neutral, half flexion, and full flexion it is possible to predict the vertebral position from surface markers by using the parameters and anthropometrical variables. In half extension this prediction is less accurate and in full extension alternative methods should be investigated for external motion capturing.