How to hideone form when 2nd form opens?

I have a form where there is a button and i want to launch an another form by the help of that button which is done but when second form opens it doesnt close the first one as i did many tries. Following is my code snippet [code] private void LoadGameButton_Click(object sender, EventArgs e) { TicTacToe tic=new TicTacToe(); tic.Show(); log = new Login(); log.Close(); // or i tried hide and different ways here but still login form appear } [/code] Please help