For nonnegative Borel measures
μ
\mu
on
R
1
R^1
and for the maximal geometric mean operator
G
f
G_f
, we characterize the weight pairs
(
w
,
v
)
(w,v)
for which
G
f
G_f
is of weak type
(
p
,
p
)
(p,p)
and of strong type
(
p
,
p
)
(p,p)
,
0
>
p
>
∞
0>p>\infty
. No doubling conditions are needed. We also note that a previously published different characterization for the strong type inequality for
G
f
G_f
has an incorrect proof.