In this paper we consider a hypothesis testing approach for detection of hiding in the least significant bit (LSB). This steganalysis problem is a composite hypothesis test-ing problem. We state a regularity condition on the image histogram, which reduces this problem to a simple hypoth-esis testing problem. We then develop a number of simple practical tests based on the estimation of the optimal log likelihood ratio statistic. We show that our tests signif-icantly outperform Stegdetect, a popular hypothesis test available in the literature. Our approach also leads to good estimates of the hiding rate.