Let \(G=SU(n,1)\), for \(n>1\), and suppose \(\Gamma\) is any nonuniform congruence subgroup of \(G\). Let \(\mu\) be the smallest non-zero eigenvalue of the Laplacian on the space of nondegenerate forms \(L^ 2(\Gamma\backslash H)\), where \(H=G/K\), \(K\)=maximal compact subgroup of \(G\). \(H\) is a complex hyperbolic \(n\)-space. Then one of the main results of the paper is the inequality \(\mu\geq 2n-1\). This is analogous to a result of Selberg for \(G=SL(2,\mathbb{R})\). And the method of proof stems from Selberg's method of nonholomorphic Poincaré series, although this paper formulates the proof adelically. Kloosterman sums appear in local computations. The A. Weil estimate of these sums is needed in one crucial case. The author conjectures that if a representation \(\pi\) is an irreducible degenerate constituent of \(L^ 2(G(\mathbb{Q})\backslash G(\mathbb{A}))\), then there exists some \(G'=U(m)\), and an automorphic representation \(\pi'\) of \(G'(\mathbb{A})\) such that \(\pi\) is the theta lifting of \(\pi'\).