Zr-based amorphous alloys exhibiting superconductivity have been found in ternary Zr85Si15−xMx and Zr85Ge15−xMx (M=B, Al, C, Si, Ge or Sn) systems by a melt-spinning technique. Specimens are in the form of continuous ribbons of 1 mm wide and 0,02 mm thick. The M content in the amorphous alloys is limited to less than 10at% B, 7 at% Al, 3 at% C, 9 at% Sn for the Zr-Si-M system and less than 7 at% B, 7 at % Al, 3 at % C and 9 at% Sn for the Zr-Ge-M system. The hardness and crystallization temperature increase significantly with the substitution of B, C or Al for Si or Ge, but the effect of the other elements is less significant. The superconducting transition temperature, 7~c, rises with the substitution of C, AI, Sn or B for Si, whereas the substitution by Ge causes a slight lowering ofTc. The effectiveness of element M on the rise ofTc decreases in the order C > Al >Sn > B >Si >Ge. The upper critical field gradient atTc,Tc, (dHc2/dT)Tc, and the electrical resistivity at 4.2 K, ϱn, decrease from 2.30 × 106 to 1.97 × 106 Am−1 K−1 and from 2.70 to 2.00 μΩm, respectively, with the amount of element M. The coefficient of low-temperature electronic specific heat,γ, land the dressed density of electronic states at the Fermi level,N*(Ef), were calculated from the experimentally measuredvalues of ϱn and (dHc2/dT)Tc using the strong-coupling theories. From the comparison ofTc with their calculated parameters, it was found that the rise ofTc with the substitution of Si by B, C, Al or Sn is caused by the increase inγ andN*(Ef). The GL parameter,k, estimated by using the GLAG theory, decreases from 100 to 78 by the substitution of elements M for Si and it is inferred that the decrease in the dirtiness is also attributable to the rise ofTc.