Collidoscope, the Prell Group’s open-source program for calculating collisional cross sections via the Trajectory Method, is now available for public use upon request. Using pdb files or simple xyz-type files, users can compute low-field collisional cross sections for many organic and biological molecules ranging in size from 100 Da to >1 MDa in helium or nitrogen gas. Parallelization is automatically implemented (though it can be turned off as needed) to speed up computations, and a built-in option automatically places positive charges on protein ions in low-energy configurations before calculating collisional cross sections.