Blinded Sample Size Re-Estimation for Binary Endpoints R package bbssr version 1.0.2 Provides comprehensive tools for blinded sample size re-estimation (BSSR) in two-arm clinical trials with binary endpoints. Unlike traditional fixed-sample designs, BSSR allows adaptive sample size adjustments during trials while maintaining statistical integrity and study blinding. Implements five exact statistical tests: Pearson chi-squared, Fisher exact, Fisher mid-p, Z-pooled exact unconditional, and Boschloo exact unconditional tests. Supports restricted, unrestricted, and weighted BSSR approaches with exact Type I error control. Statistical methods based on Mehrotra et al. (2003) <doi:10.1111/1541-0420.00051> and Kieser (2020) <doi:10.1007/978-3-030-49528-2_21>. Software Depends: R (>= 3.5.0) Imports: fpCompare, stats Suggests: testthat (>= 3.0.0), knitr, rmarkdown, dplyr, ggplot2, tibble, tidyr, Exact, exact2x2, microbenchmark Gosuke Homma <my.name.is.gosuke@gmail.com> Comprehensive R Archive Network (CRAN) Gosuke Homma [aut, cre] MIT + file LICENSE (https://CRAN.R-project.org/package=bbssr/LICENSE) 2025-06-18 application/tgz https://CRAN.R-project.org/package=bbssr doi:10.32614/CRAN.package.bbssr