Evaluation of Failure Time Surrogate Endpoints in Individual Patient Data Meta-Analyses R package surrosurv version 1.1.27 Provides functions for the evaluation of surrogate endpoints when both the surrogate and the true endpoint are failure time variables. The approaches implemented are: (1) the two-step approach (Burzykowski et al, 2001) <DOI:10.1111/1467-9876.00244> with a copula model (Clayton, Plackett, Hougaard) at the first step and either a linear regression of log-hazard ratios at the second step (either adjusted or not for measurement error); (2) mixed proportional hazard models estimated via mixed Poisson GLM (Rotolo et al, 2017 <DOI:10.1177/0962280217718582>). Software Depends: R (>= 3.5.0) Imports: copula, eha, grDevices, lme4, MASS, Matrix, msm, mvmeta, optimx, parallel, parfm, stats, survival Suggests: R.rsp, testthat (>= 3.0.0) Dan Chaltiel <dan.chaltiel@gustaveroussy.fr> Comprehensive R Archive Network (CRAN) Federico Rotolo [aut] (ORCID: <https://orcid.org/0000-0003-4837-6501>), Xavier Paoletti [ctb], Marc Buyse [ctb], Tomasz Burzykowski [ctb], Stefan Michiels [ctb] (ORCID: <https://orcid.org/0000-0002-6963-2968>), Dan Chaltiel [cre] (ORCID: <https://orcid.org/0000-0003-3488-779X>) GPL-2 2025-10-10 application/tgz https://CRAN.R-project.org/package=surrosurv doi:10.32614/CRAN.package.surrosurv