I've now completed an implementation of the option Sven requested: there's a new menu item under Edit in the model window menu, "Revise specification...". (CVS and Windows snapshot.) What it's supposed to do: Open a suitable dialog box (depending on the sort of model -- ordinary single-equation, NLS/MLE/GMM, VAR/VECM, simultaneous system -- and/or the estimator used) which contains a "clone" of the original model specification, ready for you to revise. This was quite tricky in some respects and it may not all be right yet. It's _supposed_ to respect original lag selection and any options chosen for the original model. Please let me know if it fails to do so in some cases. Implementing this for models saved in session files has required some additions to the set of information saved with models. By intent these changes are backward-compatible. In addition -- hopefully -- if gretl can't get all the info it wants from older session files the "Revise" option will degrade gracefully, i.e. the clone specification may not be exact, but shouldn't be too far off. Note that by the design of the gretl model dialog (which is estimator-specific) you can't use this mechanism to estimate "the same specification" as a previous model but using a different estimator. But you might get an approximation to this if you "prime" the model dialog by re-estimating the old specification using "Revise", then open the model dialog again. Some aspects of the dialog are "sticky" and will persist across choices of estimator. Allin.