Hi, I am using pthread_kill() system call by including pthread.h, while compiling it is saying, pthread_kill:undefined reference. I compiled with gcc -lpthread and gcc -pthread..still problem was not resolved..saying undefined reference... In pthread.h also it seems that this call is not defined. I am using Redhat 9. what is the solution to this problem...how can use pthread_kill() call. Thanks, Anil.