Abstract Summary: We describe handalign, a software package for Bayesian reconstruction of phylogenetic history. The underlying model of sequence evolution describes indels and substitutions. Alignments, trees and model parameters are all treated as jointly dependent random variables and sampled via Metropolis–Hastings Markov chain Monte Carlo (MCMC), enabling systematic statistical parameter inference and hypothesis testing. handalign implements several different MCMC proposal kernels, allows sampling from arbitrary target distributions via Hastings ratios, and uses standard file formats for trees, alignments and models. Availability and Implementation: Installation and usage instructions are at http://biowiki.org/HandAlign Contact: ihh@berkeley.edu Supplementary information:Supplementary material is available at Bioinformatics online.