The structural and superconducting properties of the series, Bi2−xPbxSr2−yLayCuO6+δ (x=0.5, 0⩽y⩽1.0 and 0⩽x⩽1.0, y=0.4), are studied. X-ray diffraction experiments show both series form a solid solution with a non-modulated orthorhombic structure over a wide range. Resistivity data shows metallic behavior and superconductivity with a maximum of Tc=29.5 K at x=0.6, y=0.4. The appearance of superconductivity correlates well with an oxygen content of 6 as measured by iodometric titration. A semiconducting-metallic-semiconducting transition was observed and kinks exist in both T c versus x ( or y) and ϱ ϱ 290 versus x ( or y) curves. The fact that simultaneous substitution of Pb and La for Bi and Sr is necessary to stabilize the 30 K superconducting phase may indicate the importance of preventing structural disorder arising from Bi substitution onto the Sr site.