This paper develops and implements semiparametric methods for estimating binary response (binary choice) models with continuous endogenous regressors. It extends existing results on semiparametric estimation in single index binary response models to the case of endogenous regressors. It develops a control function approach to account for endogeneity in triangular and fully simulataneous binary response models. The proposed estimation method is applied to estimate the income effect in a labor market participation problem using a large micro data set from the British FES. The semiparametric estimator is found to perform well, detecting a significant attenuation bias. The proposed estimator is contrasted to the corresponding Probit and Linear Probability specifications.