This paper discusses a longitudinal study that explored the relationship between use of organizational memory and knowledge (OM/K) and knowledge worker productivity within the engineering group at a nuclear power plant. Three data points were taken over five years. An OM/K System (OM/KS) was identified that improved effectiveness/productivity of the organization. The basic components of the OM/KS remained the same over the study. A key and unexpected finding was that new members of the organization did not consider the OM/KS as effective as established members and tended not to use the system until they became established members themselves. To explain the success of the OM/KS, DeLone and McLean’s IS Success Model was adapted to OM/KS.