Given a finite group
G
G
, the symmetric genus of
G
G
is defined to be the smallest integer
g
g
such that
G
G
acts faithfully on a closed orientable surface of genus
g
g
. Previous to this work, the task of determining the symmetric genus for the sporadic simple groups had been completed for all but nine groups:
J
3
{{\text {J}}_3}
,
McL
\operatorname {McL}
,
Suz
\operatorname {Suz}
,
O’N
{\text {O’N}}
,
Co
2
\operatorname {Co}_2
,
Fi
23
\operatorname {Fi}_{23}
,
Co
1
\operatorname {Co}_1
,
B
{\text {B}}
, and
M
{\text {M}}
. In the present paper the authors resolve the problem for six of these groups, viz.
J
3
{{\text {J}}_3}
,
McL
\operatorname {McL}
,
Suz
\operatorname {Suz}
,
O’N
{\text {O’N}}
,
Co
2
\operatorname {Co}_2
, and
Co
1
\operatorname {Co}_1
. Significant progress is also reported for the group
Fi
23
\operatorname {Fi}_{23}
.