Several theorems are presented which characterize Goppa codes having the property of becoming cyclic when an overall parity cheek is added. If such a Goppa code has location set

and a Goppa polynomial

that is irreducible over

, then

must be a quadratic. Goppa codes defined by

and location set

with cardinality

such that

are considered along with their subcodes. A sufficient condition on

is derived for the extended codes to become cyclic. This condition is also necessary when

= 1. The construction of

for different

satisfying the stated condition is investigated in some detail. Some irreversible Goppa codes have been shown to become cyclic when extended by an overall parity check.