Thank you. I should have thought about that :)
In your case tot is not shared with the kernels:
rand = {1, 2, 3, 4, 5, 6}; f = x^2; SetSharedVariable[tot] tot = ConstantArray[0, 6]; ParallelDo[ Ff = f /. x -> rand[[i]]; tot[[i]] = Ff; , {i, 1, 6, 1} ]; totT = Total[tot]
now it should work...
