The authors study various types of stability of the functional differential equations \(x'(t)=F(t,x_ t)\) where \(x_ t(s)=x(t+s),\)- h\(\leq s\leq 0\), and h is a positive constant. The main tool is the Lyapunov functionals. These functionals satisfy certain conditions involving functions which verify Jensen's inequality. Many concrete illustrative examples are given to illustrate the theory.