Thanks. You are right about the Maximum Likelihood Estimation. Still, I think Probit quacks a little more like Discriminant Analysis, and I would call it a classification technique. With binary variables, one cannot simply transform the 0 - 1 and then enter a transformed value as a dependent variable. Without defining what "is is" or what "really a regression" is, I am hoping to stimulate more interest in a technique (probit and logit) that has much merit and that sometimes gets glossed over as a half-page addendum to text chapters on regression. (The link supporting the "not really a regression comment" also provides some explanation.) But those who call it probit regression would certainly agree with your comment.