The problem of computing packet error probabilities caused by a combination of noise at the receivers and interference between packet transmissions is discussed. An upper bound on the packet error probability induced in direct-sequence spread-spectrum networks is computed. The bound is valid independently of whether signals arrive with equal or unequal powers at the receiver site. It has a simple form, is easy to compute, and is valid for various classes of forward error correction codes (e.g. BCH, convolutional codes).< >