NeuronGrowth is a Java-based software tool designed for semi-automated quantification of neurite extension and retraction from sequences of digital time-lapse series of images. NeuronGrowth can be applied to image sequences acquired under phase contrast, differential interference contrast (DIC) and fluorescence optics. NeuronGrowth is a multiplatform software that runs on PC, Mac or Linux systems, as a plug-in for the free software ImageJ.