We propose a partitioned-bus architecture with a variable-width-bus scheme to reduce power consumption in bus lines in VLSIs. The partitioned-bus architecture (horizontal partitioning) restricts bus driving range to minimal, while the variable-width-bus scheme (vertical partitioning) uses additional tag lines so as to automatically indicate effective bus width with-out driving unnecessary bus lines depending on data to be transferred. Applying this method to a general purpose microprocessor, we demonstrate 30% and 35% power consumption reduction in bus lines, respectively for the partitioned-bus architecture and the variable-width-bus scheme, compared with the conventional bus architecture. Combining the both together, we show about 55% power consumption reduction in bus lines for typical applications. Increase in chip area for this architecture is about 30% compared with the conventional bus architecture.