Many software systems have been produced in hostconcentrated development environments. At present, the software development environment has been changing into a distributed one because of the progress of WS (workstation) and network computing technology. Information network systems have also been expanding more and more with the progress of such network computing technology. For instance, basic CSSs (client/server systems) which have two-layer structure have been expanded to N layers, since such CSSs can be easily and rapidly introduced into software development processes at low cost. In this paper, we discuss a software reliability growth model which evaluates the software quality quantitatively in the system testing phase of the distributed development environment. In particular, the model assumes that the software system consists of n reused software components and m newly developed software components. We derive a new software reliability growth model which aids in management of the development of a quality and reliable software system in a distributed development environment. We introduce weight parameters into our model in order to represent the proportion of the total testing load for each software component. We also perform sensitivity analysis for various software reliability assessment measures by using the actual faultdetection count data.