This is the first time I ask a question. I have seen many solutions to this error and tried but they are not working. Here is the code. Needs["DifferentialEquations`NDSolveProblems`"]; Needs["DifferentialEquations`NDSolveUtilities`"]; Needs["FunctionApproximations`"]; Clear["Global`*"]; e = 1.60217662*10^-19; c = 299792458; m = 9.10938356*10^-31; \[Epsilon]0 = 8.854187817*10^-12; A = 10^17; h = 6.62607004*10^-34; hbar = 1.0545718*10^-34; k = 1/\[Epsilon]0 (2 e/h^3) (4 Pi/3); x0 = (3/(4 *Pi)* A*1.60439572*10^-24/(4*10^14))^(1/3)/100; xf = 10^0; s = NDSolve[{1/x D[x y[x], {x, 2}] == k ((e y[x]/c)^2 + 2 m*e y[x])^1.5, y[x0] == 10^6, y[xf] == 10^-5}, y[x], {x, x0, xf}] xf should be infinity but NDSolve doesn't allow infinity so I put a relatively large number. y[xf] is also needed to be zero at infinity. I put a relatively small number since I expected that y[x] is close to zero when x is approaching infinity. Here is the error: At x == 0.112455460174063`, step size is effectively zero; singularity or stiff system suspected. >>