The Global System for Mobile (GSM) communication is the Second Generation of mobile technology. Although the world is moving towards Third and [[wysiwyg_imageupload::]]Fourth generation but GSM has been the most successful and widespread technology in the communication sector. GSM technology paved a new way for mobile communication.This project explains the interfacing of a GSM Module with a PIC microcontroller. It also covers a way to dial a particular GSM mobile number as well as send a message to it using AT Commands with the help of PIC18F4550.As explained earlier (refer GSM interfacing with 8051), a line converter MAX232 is employed to convert the RS232 logic data of GSM Module to TTL logic so that it can be processed by the microcontroller. In this project, instead of RS232 logic data, TTL logic output has been taken and thus PIC18F4550 has been directly connected with GSM Modem without any line converter in between. The following diagram shows the TTL input and output of GSM modem used.