In spread spectrum acquisition systems, the threshold voltage is considered as one of the main parameters that affect the mean acquisition time. This important parameter is set, normally, to a constant value optimized from specific channel environments and minimum signal detect ability at the receiver acquisition system. Any change in the channel environments or signal level, requires a change in the threshold level. In this project, an adaptive threshold technique for direct-sequence spread spectrum signals is proposed, analyzed and tested experimentally. The performance of the proposed acquisition technique, in terms of the mean acquisition time, is evaluated, in the presence of white Gaussian noise and narrowband interference. Also, a comparison is made, in terms of the mean acquisition time, with a system that carries the same features as the proposed adaptive acquisition system, but with constant threshold setting. The proposed adaptive threshold acquisition technique, has proved to be faster, in terms of the mean acquisition time, than constant threshold acquisition technique. Significant improvements are gained, especially, in high interference environments. An experimental system for direct-sequence signal acquisition system utilizing a digital sliding correlator and simple stepped serial search strategy, is designed and implemented. The adaptive threshold system is designed and implemented experimentally using the digital signal processor TMS320C25. Experimental and theoretical results compare well.