Microstructure, thermal, electrical and mechanical properties of penta Bi- Sn- Pb based alloys have been investigated. Matrix structure (Formed crystalline phases) and measured physical properties of Bi- Sn- Pb- In- X (X= Cd/or Zn) penta alloys changed with varying composition. The new penta fusible, Bi50Pb15Sn22Cd3In10, alloy has best properties such as high density, low melting point and friendly environmental, (reduced toxicity elements Pb and Cd by 40% and 75%, compared used alloys), for shielding blocks in mega-volt radiotherapy. The melting temperature of Bi50Pb15Sn22Cd3In10 alloy is ~58 ?C and it is density is 10.117 gm/cm3. The elastic modulus of Bi50Pb15Sn22Cd3In10 is 29.03 Gpa. Vickers hardness and internal friction values of Bi50Pb15Sn22Cd3In10 alloy are 9.72 Kg/mm2 and 0.085. The Bi50Pb15Sn22Cd3In10 alloy consists of rhombohedral Bi phase, tetragonal Sn phase, face centered cubic Pb phase, hexagonal Cd phase, face centered cubic In phase, Pb7Bi3 and SnBi intermetallic compounds.