ASreml 4


Analysing data with all new ASReml 4

ASReml 4, the outstanding data analysis software designed for fitting linear mixed models is now available for download. Already widely used by scientists and researchers in the biosciences the new procedures and functionality added at version 4 will further extend ASReml’s ability to analyse large datasets and complex statistical models.

The main development is the introduction of an alternative functional method of associating variance structures with random model terms and the residual, akin to that used in ASReml-R, as an alternative to the former structural method, where the variance models were specified separately from the model terms. Using the functional specification, the variance model for random model terms and the residual error term is specified in the linear mixed model by wrapping terms with the required variance model function. The functional approach leads to a simpler, more concise and less error-prone specification of the linear mixed model, that is more automatic for specifying multi-section residual variances.

There are also many smaller changes, to improve efficiency and convenience. These include:

  • computationally efficient fitting of random regression models when there are more variables than observations,motivated by the use of SNP marker data to explain genotypes
  • fitting linear relationships among variance structure parameters
  • automatic generation of initial values for variance parameters
  • generating a template to allow an alternative way of presenting
  • parametric information associated with variance structures
  • new qualifiers !ASSIGN, !FOR and !IF to simplify job flow,
  • stabilized updates to improve convergence of factor analytic models,
  • enhanced syntax for VPREDICT, allowing specification of functions in terms of names rather numbers
  • calculating information criteria
  • writing out design matrices to external files

Users are supported by VSNi (if they have a support contract), a range of tutorials and user guides and by an active user community through the ASReml Forum. For more details on ASReml, see the new features page.

Free Upgrade

Users with current support contract or annual license are automatically entitled to this upgrade. The license software has been updated to the latest version but existing license keys should continue to work with ASReml 4, so long as the Support Version code is 1607 or higher. The License Guide explains how you can check your key and what changes might be needed, if any.


ASReml 4 is supported on the same platforms as ASReml 3. The download procedure is the same as before.


ASReml 4 downloads have been updated for Linux – please read the notes on the downloads page before installing.


To trial any of our software, please send an email to support detailing:

  • Which software you wish to trial
  • Your name
  • Your organisation
  • Your email address
  • Telephone number
Please note –  students requiring trials please arrange for your lecturer or supervisor to contact us. We would be happy to advise on the appropriate tools on offer.