This was an FDA/SAS bargain a long while ago. SAS made the XPT format publicly available and unchanging in return for it becoming a standard for submission. Many packages can reliably read or write these files. (The same is not true for other SAS file formats, nor is xport the SAS default.) I do not know how good the R routines are, having never used them. The following snippit is taken from http://www.fda.gov/downloads/ForIndustry/DataStandards/StudyDataStandards/UCM312964.pdf 2 Dataset Specifications 2.1 File Format SAS XPORT transport file format, also called Version 5 SAS transport format, is an open format published by the SAS Institute. The description of this SAS transport file format is in the public domain. Data can be translated to and from this SAS transport format to other commonly usedformats without the use of programs from SAS Institute or any specific vendor. Sponsors can find the record layout for SAS XPORT transport files through SAS technical support technical document TS-140. This document and additional information about the SAS Transport file layout can be found on the SAS World Wide Web page at http://www.sas.com/fda-esub. --- Said document TS-140 talks about IBM 360 and Dec VAX machines but no others, which should give you an idea of its age. Terry Therneau On 09/27/2015 05:00 AM, r-help-request at r-project.org wrote:> Peter > > Thanks for the explanation. One further comment ? you wrote: >> >I don't think the FDA "requests" XPT files > In fact, they do make such a request. Here is the actual language received this week (and repeatedly in the past): >> >Program/script files should be submitted using text files (*.TXT) and the data should be submitted using SAS transport files (*.XPT). > Dennis