Programs for Computing Group Sequential Boundaries Using the Lan-DeMets Method,
Version 2.1, Last Update: 11/17/2003


FORTRAN programs for the computation of boundaries and exit probabilities in the sequential analysis of clinical trials are described. The computations are appropriate for any trial based on normally distributed test statistics with independent increments, including those in which patients give a single continuous or binary response, survival studies, and certain longitudinal designs. Interim analyses need not be equally spaced, and their number need not be specified in advance. In addition to boundaries, power computations, probabilities associated with a given set of boundaries, and confidence intervals can be computed. An explanation of the input and output, along with some verbatim transcripts of interactive sessions are included. Some theoretical background and description of the numerical computations is provided in the documentation appendix. The program and this documentation are updates of earlier versions.


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Binaries and source:

  • Works on Windows 7 and 10 with java 1.7 or higher
  • This is a Microsoft Windows graphical user interface for ld98.

    Download the WinLD-2.1.1.exe file and run it to install WinLD. By default it will install into C:\WinLD, however, you do have the option to change the destination. It will also create a folder in All Programs called WinLD with the shortcut to the program itself (WinLD) inside.

To compile: {gfortran -o ldbnds ldbnds.f}:


Windows Compatibility:

The LanDeMets DOS (.exe) software is widely compatible with Windows 98 through Windows 10. WinLD (Microsoft Windows graphical user interface for ld98) and ld98.exe work fine even in Windows 10 (although you have to tell it that you really do want to run the program even though Windows doesn’t know if it’s “safe”).

The ldbnds.exe program, however, will not run in Windows 8 or above.

The latest version of LanDeMets WinLD is 2.1.1. This provides a Windows 10 graphical interface and allows you to export the results to a Microsoft Word document.


  1. David M. Reboussin, Department of Public Health, Bowman Gray School of Medicine, Winston-Salem, NC 27157
  2. David L. DeMets, Department of Biostatistics and Medical Informatics, Department of Statistics, University of Wisconsin, Madison, WI 53706
  3. KyungMann Kim, Department of Biostatistics and Medical Informatics, Department of Statistics, University of Wisconsin, Madison, WI 53706
  4. K. K. Gordon Lan, Pfizer Central Research, Groton, CT 06340

Program for Computing Sample Size, Version 1.0, Last Update: 2/25/2004


SampleSize was developed using Sun’s Java2 programming language. It is being distributed as a Java Archive File (JAR), which should  execute on most MS Windows systems without any additional software installation. Simply download the jar into a folder (e.g., C:\SampleSize) and create a shortcut to it on your desktop. However, if it does not run you will need to download the Java2 Runtime Environment from Sun’s Java web site. A link to the download area is provided in the “Program” area. Also, since this program is in Java, you can run it on any system that has a Java Runtime Environment (v1.4.1 or higher). Visit Sun’s Java web site
for more information.

If you need to include the output from this program in a word processor, it is recommended that you “Print” to an Adobe PDF file and then use Acrobat to copy the table (using “Select Table”) or the graph (using “Select Image”) and then paste either into your document.


Friedman LM, Furberg CD, DeMets DL: Fundamentals of Clinical Trials, Third Edition, New York, 1998, Springer-Verlag


  • Click Here to download the SampleSize program (v1.02)
  • Click Here to download the SampleSize program (v1.01)
  • The SampleSize Manual is no longer available
  • If SampleSize does not run, you may need a different version of Java.
    the Java2 Windows Runtime Environment v1.4.2. Select the “Windows Installation, Multi-language” download. After clicking the “Download” link for the JRE, a dialog box pops up — choose the “Open” option. This will prompt you through the steps to download. (The letters “iftw” mean “install from the web”.) If you wish to install the package offline, select the “Windows Offline Installation, Multi-language” download and save the file to disk. Install per instructions
  • Download the Java2 Runtime
    Environment. Select the J2SE v1.4.2 or higher JRE. Install per instructions