A connector system for an implantable lead, which includes a header having a lumen for receiving the implantable lead. The lumen defines a mating surface and has an internal diameter larger than the lead to be connected therein. A collar is slidably engageable with the lead. Part of the collar is slidable into the header lumen, and part of the collar is releasably securable to the header such that the lead is retained in the lumen. The part of the collar that is slidable into the header lumen may be tapered. The tapered part of the collar and/or the mating surface may be formed of a compressible material.