Let W(t) be a Wiener path, let $xi;:;[0,;{infty}); o;mathbb{R}$ be a continuous and increasing function satisfying $xi$(0) > 0, let $$T_{/xi}=inf{t{geq}0;:;W(t){geq}xi(t)}$$ be the first-passage time of W over $xi$, and let F denote the distribution function of $T_{xi}$. Then the first passage problem has a unique continuous solution as following $$F(t)=u(t)+{sum_{n=1}^infty}int_0^t;H_n(t,s)u(s)ds$$, where $$u(t)=2Psi(xi(t)/sqrt{t});and;H_1(t,s)=dPhi;({xi(t)-xi(s)}/sqrt{t-s})/ds;for;0;{leq};s