Atomic hydrogen, the simplest of all stable atoms, has been a challenge to spectroscopists and theoreticians for many years. Here, as in similar systems like positronium, muonium and possibly helium, the accuracy of theoretical predictions is comparable to that of experimental measurements. Hence exciting confrontations are possible. This together with expected large experimental improvements explains the strong interest in the symposium held in Pisa in June-July 1988. The resulting book completely covers the precision spectroscopy of atomic hydrogen and hydrogen-like systems, and also discusses aspects of QED and the influence of strong fields.