R package multimark. Traditional and spatial capture-mark-recapture analysis with multiple non-invasive marks. The models implemented in ’multimark’ combine encounter history data arising from two different non-invasive “marks”, such as images of left-sided and right-sided pelage patterns of bilaterally asymmetrical species, to estimate abundance and related demographic parameters while accounting for imperfect detection. Bayesian models are specified using simple formulae and fitted using Markov chain Monte Carlo. Addressing deficiencies in currently available software, ’multimark’ also provides a user-friendly interface for performing Bayesian multimodel inference using non-spatial or spatial capture-recapture data consisting of a single conventional mark or multiple non-invasive marks.