Distance-sampling is a popular method for estimating density and abundance of organisms in ecology. Rdistance contains routines that assist with analysis of distance-sampling data collected on point or line transects. Distance models are specified using regression-like formula (similar to lm, glm, etc.). Abundance routines perform automated bootstrapping and automated detection-function selection. Overall (study area) and site-level (transect or point) abundance estimates are available. A large suite of classical, parametric detection functions are included along with some uncommon parametric functions (e.g., Gamma, negative exponential) and non-parametric smoothed distance functions. Custom (user-defined) detection functions are easily implemented (see vignette). The help files and vignettes have been vetted by multiple authors and tested in workshop settings.