A behavior of (P)L1-principal
functions on some compactifications of a Riemann surface is studied. The main result
in this paper is that a (P)L1-principal function is extended almost everywhere
continuously to some compactifications and the extention is almost everywhere
constant on each part of P. If the genus of the surface is finite and P is the
canonical P,(P)L1-principal function can be extended continuously to the
Kerékjártó-Stoilow compactification.