The Wireless Application Protocol (WAP) is a protocol stack for wireless communication networks. WAP uses WTLS, a wireless variant of the SSL/TLS protocol, to secure the communication between the mobile phone and other parts of the WAP architecture. This paper describes the security architecture of WAP and some important properties of the WTLS protocol. There are however some security problems with WAP and the WTLS protocol. Privacy, data protection and integrity are not always provided. Users and developers of WAP-applications should be aware of this. In this paper, we address the security weaknesses of WAP and WTLS and propose some countermeasures and good practices when using WAP. We conclude with advising when to use WAP and when not.