Linear least squares estimation techniques can be used to enhance suppression of narrowband interference in direct-sequence spread-spectrum systems. Nonlinear techniques for this purpose have also been investigated recently. Here, we derive maximum-likelihood receivers for direct-sequence signal in Gaussian interference with known second order characteristics. It is shown that if the receiver uses samples from outside the bit interval, then the receiver structure (called ML II)is nonlinear. The bit error rate performances of these ML receivers are compared to those of linear receivers employing one-sided and two-sided least squares estimation filters, for the case of Gaussian autoregressive interference, It is shown that the ML II receiver outperforms the matched filter, the one sided and the two sided transversal filters.