An adaptive filter configuration, known as the adaptive line enhancer (ALE), has previously been suggested by Widrowet al. for the detection of sinusoidal signals in wideband noise. Very few results are available in the literature on the analysis and performance of the ALE for the case of correlated noise. In the paper we analyse the ALE response to a sinusoid in 1-pole lowpass noise and show that there exists an optimum value of the decorrelation parameter. An attempt has been made to study the effect of the correlation of the lowpass noise on the coupling between the positive and negative frequency components of the sinusoid, and the response of the ALE to low- and high-frequency sinusoids. The ALE has been simulated using the recently derived lattice structure and the recursive least-squares lattice algorithms. The results agree closely with those of the theoretical predictions.