One of my friend,who used to talk to me a lot but last 3 to 4 months he is not giving attention to me.I tried to call him once ,He said that he would call back to me.now one month is over... I am waiting for his call?there is no problem within us then also why is he behaving like this?

How would we know? We don't know your ages, your genders, anything about your friendship. Maybe he has new friends, or a girlfriend, or a boyfriend if gay, or his pet died, or his family is having serious problems and needs his help. There are almost infinite reasons. Make at most 2 or 3 attempts to say you miss him and hope he's OK, and then give up. This will happen a lot throughout life.

THis happens... friends drift into your life... friends drift out of your life... but family is always family. You live with it because that's how life is. There are very few constants... everything changes.

You have to remember too, that a friendship is never one-sided. You no longer have a friendship at all with him.

For the above reasons already said, consider the friendship over.