This technical report introduces EZR, a free, user-friendly statistical software package designed for medical statistics, particularly in hematopoietic stem cell transplantation (HSCT) research. EZR is based on R and R Commander, offering a range of statistical functions commonly used in clinical studies, including survival analysis, competing risk analysis, time-dependent covariate analysis, receiver operating characteristics (ROC) analysis, meta-analysis, and sample size calculation. It is freely available on the authors' website and compatible with both Windows and Mac OS X. The report highlights that while many commercial statistical packages are widely used in medical statistics, they often lack specific functionalities required for HSCT research, such as competing risk analysis and time-dependent covariates. EZR addresses these gaps by providing a graphical user interface that allows users to perform complex statistical analyses through point-and-click operations, making it more accessible to clinicians. Installation instructions for EZR on Windows and Mac OS X are provided, along with basic operations, including creating, modifying, and saving data sets. The software also includes functions for descriptive statistics, statistical analysis of categorical and continuous variables, survival analysis, and competing risk analysis. EZR supports a wide range of statistical tests, including survival analysis, Cox proportional hazards regression, and Fine-Gray regression for competing risks. The report emphasizes that EZR is a valuable tool for researchers and clinicians in HSCT studies, offering a user-friendly interface and a comprehensive set of statistical functions. It is freely available and can be used for data analysis, with results that can be saved and shared. The software is also compatible with various data formats, including Excel and CSV files, and supports advanced statistical analyses such as stepwise variable selection and regression modeling. The report concludes that EZR is a suitable alternative to commercial statistical software for medical research, particularly in the field of HSCT.This technical report introduces EZR, a free, user-friendly statistical software package designed for medical statistics, particularly in hematopoietic stem cell transplantation (HSCT) research. EZR is based on R and R Commander, offering a range of statistical functions commonly used in clinical studies, including survival analysis, competing risk analysis, time-dependent covariate analysis, receiver operating characteristics (ROC) analysis, meta-analysis, and sample size calculation. It is freely available on the authors' website and compatible with both Windows and Mac OS X. The report highlights that while many commercial statistical packages are widely used in medical statistics, they often lack specific functionalities required for HSCT research, such as competing risk analysis and time-dependent covariates. EZR addresses these gaps by providing a graphical user interface that allows users to perform complex statistical analyses through point-and-click operations, making it more accessible to clinicians. Installation instructions for EZR on Windows and Mac OS X are provided, along with basic operations, including creating, modifying, and saving data sets. The software also includes functions for descriptive statistics, statistical analysis of categorical and continuous variables, survival analysis, and competing risk analysis. EZR supports a wide range of statistical tests, including survival analysis, Cox proportional hazards regression, and Fine-Gray regression for competing risks. The report emphasizes that EZR is a valuable tool for researchers and clinicians in HSCT studies, offering a user-friendly interface and a comprehensive set of statistical functions. It is freely available and can be used for data analysis, with results that can be saved and shared. The software is also compatible with various data formats, including Excel and CSV files, and supports advanced statistical analyses such as stepwise variable selection and regression modeling. The report concludes that EZR is a suitable alternative to commercial statistical software for medical research, particularly in the field of HSCT.