Abstract: A modular valve assembly is formed from multiple modular valves having a valve base and a valve actuator. Each base includes at least a first channel and a second channel and an internal passage forming an opening in the first channel so as to be in selective fluid communication with an exterior port of the valve base, and with the second channel being a through passage that is not in fluid communication with the internal passage. Adjacent valve bases are interconnectable in one of two orientations either with the first and second channels of one valve base being aligned with the first and second channels, respectively, of an adjacent valve base, or with the first and second channels of one valve base being aligned with the second and first channels, respectively, of an adjacent valve base. The valve bases may be provided with third and fourth channels for three-way operability.