This is a single-center, double-blind, randomized, six-period, cross- over trial conducted on six study days. On each of the six study days, each subject (total of 16) will receie a single dose of .2 U/kg dose of either NN304 or human NPH insulin. Blood samples will be taken over a period of 24 hours. The objectives of this trial are to compare the intra-subject and inter-subject variability of kinetic profiles after injections in healthy male volunteers.