Spatial-phase locked electron beam lithography (SPLEBL) provides feedback control of electron beam position by monitoring the signal from a fiducial grid on the substrate. Continuous, or "real-time," spatial-phase locking has been investigated for raster-scan Gaussian beam and for shaped-beam systems. Discontinuous feedback, or "look-then-write," techniques have been implemented for vector-scan systems. However, it would be advantageous to provide real-time spatial-phase locking for vector-scan systems because of their wide adoption for research, prototyping, and specialty device production. Here, the authors present a phase locking algorithm, performance simulations, and initial experimental results for real-time, vector-scan SPLEBL. The authors demonstrate that real-time, vector-scan SPLEBL can provide subnanometer precision phase locking for different feature filling strategies, exposure parameters, and pattern geometries using reasonable data lengths and practical grid signal-to-noise ratios. (c) 2007 American Vacuum Society.