The paper reviews many of the coding techniques which have been proposed for use in spread-spectrum communication links. In these systems, narrow-band data accesses a common wideband channel, with each subscriber assigned to a unique access code. This code division multiple access (CDMA) system permits uncoordinated access to the channel with the interference level set by the total number of active subscribers. The paper investigates pseudo-noise (PN) and related sequence sets, specifically the auto- and crosscorrelation responses are examined both with and without data transmissions. These are quantified in terms of peak sidelobe errors, characteristic probability density functions and bit error ratio performance in the CDMA multi-user traffic environment. This allows the CDMA capacity to be predicted given the bit rate requirements, total available bandwidth and required bit error ratio