What is a normal blood pressure reading for a 4 year old child?

Important question. 90/60 would be the normal. I have seen many childen with a blood pressure of e.g. 110/0. It is the difference between the two pressures (pulse pressure) that is important in kids and few pediatricians measure blood pressure. It gives a lot of information about the autonomic nervous system that is so easily affected by the usual "junk" that is is considered to be their birthright.