AbstractWWW-based user interface is presented for secure electronic mail service for healthcare users. Using this method, communications between an electronic mail (WWW) server and users (WWW browsers) can be performed securely using Secure Socket Layer protocol-based Hypertext Transfer Protocol (SSL-HTIP). The mail can be encrypted, signed, and sent to the recipients and vice versa on the remote WWW server. The merit of this method is that many healthcare users can use a secure electronic mail system easily and immediately, because SSL-compatible WWW browsers are widely used and this system can be made available simply by installing a WWW-based mail user agent on a mail server. We implemented a WWWbased mail user agent which is compatible with PEM-based secure mail and made it available to about 16,000 healthcare users. We believe this approach is effective in facilitating secure network-based information exchange among medical professionals.