You need to include more information. Are you asking about a web form or a PDF form? What would be the source of the data you want autofilled? The more info your provide, the better.
What about autofilling an email adress field, based on a previous field (e.g. drop-down list of names)? If the relationship between the name and email address can be imputed somehow, this would be a great tool for making the form quicker to fill and reducing response error.