The Nevanlinna-Pick problem on a reproducing kernel space is known to be solvable if and only if the Nevanlinna-Pick matrix is nonnegative. In this paper, we give a constructive proof showing the determinant of the matrix is nonnegative is already equivalent to the solvability of the problem. Then we obtain formulas for the minimal norm among solutions and consequences concerning interpolating values. Mathematics Subject Classification: 46E22