In continuation with these previous studies, this study investigates the effects of inclination angles on foam rheology in pipes within the context of two-flow-regime concept. The results showed that foam rheology was not significantly altered as long as the slug flow or plug flow pattern was formed because of a viscous-force dominant environment. However, if flow conditions fell within the segregated flow pattern, foam rheology was governed by the gravitational force rather than the viscous force, and therefore the flow characteristics were sensitive to inclination angles. These findings were supported by visual observations as well as pressure responses.