A Method for Finding the Least Squares Estimate of the Intersection Point of Two Helices in Space When the helical trajectories of two charged particles moving away from a common point in a magnetic field are reconstructed from measurements on the tracks, the reconstructed tracks are perturbed by measurement and other errors and do not, in general, intersect. A method is given for adjusting the reconstructed tracks in a least squares manner so that they do intersect. CACM April, 1966 Royston, R. J. Gregory, J. CA660406 JB March 3, 1978 10:42 AM 1443 5 1443 1443 5 1443 1443 5 1443