+\fB\-\-group\fR=\fINAME\fR[:\fIGID\fR]
+Force \fINAME\fR as group for added files. If \fIGID\fR is not
+supplied, \fINAME\fR can be either a user name or numeric GID. In
+this case the missing part (GID or name) will be inferred from the
+current host's group database.
+
+When used with \fB\-\-group\-map\fR=\fIFILE\fR, affects only those
+files whose owner group is not listed in \fIFILE\fR.
+.TP
+\fB\-\-group\-map\fR=\fIFILE\fR
+Read group translation map from \fIFILE\fR. Empty lines are ignored.
+Comments are introduced with \fB#\fR sign and extend to the end of line.
+Each non-empty line in \fIFILE\fR defines translation for a single
+group. It must consist of two fields, delimited by any amount of whitespace:
+
+.EX
+\fIOLDGRP\fR \fINEWGRP\fR[\fB:\fINEWGID\fR]
+.EE
+
+\fIOLDGRP\fR is either a valid group name or a GID prefixed with
+\fB+\fR. Unless \fINEWGID\fR is supplied, \fINEWGRP\fR must also be
+either a valid group name or a \fB+\fIGID\fR. Otherwise, both
+\fINEWGRP\fR and \fINEWGID\fR need not be listed in the system group
+database.
+
+As a result, each input file with owner group \fIOLDGRP\fR will be
+stored in archive with owner group \fINEWGRP\fR and GID \fINEWGID\fR.