In the present investigation, we introduce and investigate a new subclass of the function class Sigma of bi-univalent functions defined in the open unit disc. We find estimates on the coefficients vertical bar a(2)vertical bar and vertical bar a(3)vertical bar for functions in the function class S-Sigma (n, h, lambda). The results presented in this paper improve or generalize the recent works of Jothibasu [13] and other authors.