GSM has been an important part in mobile communications over the last decade. Today, it has been developed to satisfy new demands in true broadband services. One of its great strengths is the international roaming capability of giving consumers seamless services in many countries. GSM has been a vital driver in growth, with more than 450 million GSM users in the world. This presentation will focus on the antenna designs in slider phone for GSM900/GSM1800 operations. Some antenna designs such as PIFA, helix antenna and shorted monopole antenna in clamshell, bar and slider phones will be introduced. And, a shorted monopole dual band antenna for ultra-thin profile slider phones will be presented and discussed.