Bit error patterns for high speed data systems are generated by randomly distributing a first error pattern of G bits, output from a group of substantially uncorrelated bit error generators, into a second error pattern of N bits, where G and N are integers and G is less than or equal to N. In one embodiment, G bit error generators produce a G bit error pattern per bit period. Each bit error generator operates at a prescribed bit error rate. A distribution element randomly rearranges the order and placement of the G bits produced during a single bit period within an N bit grouping. The N bit group corresponds to N consecutive bits of data with which the error bits can be combined. Each bit error generator can be realized by a linear feedback shift register or its equivalent. Different primitive polynomials and different lengths can be used for each linear feedback shift register. In addition, outputs from fewer than all the shift register stages are utilized to generate each error bit.