The phase behavior of ternary poly-(2-vinylpyridine) (P2VPy)/poly-(N-vinyl-2-pyrrolidone) (PVP)/bis-(4-hydroxyphenyl)methane (BHPM) blends was studied. Fourier transform infrared spectroscopic examinations demonstrated that BHPM interacts with P2VPy and PVP through hydrogen-bonding interactions. The addition of a sufficiently large amount of BHPM transformed an opaque blend with two glass-transition temperatures (T-g's) to a transparent single-T-g blend, Scanning electron microscopic studies showed that the transparent single-T-g blend is micro-phase-separated at a scale of about 30 nm.