diff --git a/doc/Makefile.in b/doc/Makefile.in
index fe81249..677a3f7 100644
--- a/doc/Makefile.in
+++ b/doc/Makefile.in
@@ -50,6 +50,7 @@ OBJECTS=CK_ARRAY_FOREACH		\
 	ck_bitmap_set			\
 	ck_bitmap_test			\
 	ck_bitmap_base			\
+	ck_bitmap_union			\
 	ck_bitmap_size			\
 	ck_bitmap_clear			\
 	ck_bitmap_bits			\
diff --git a/doc/ck_bitmap_union b/doc/ck_bitmap_union
new file mode 100644
index 0000000..b0ab8e8
--- /dev/null
+++ b/doc/ck_bitmap_union
@@ -0,0 +1,58 @@
+.\"
+.\" Copyright 2012-2014 Samy Al Bahra.
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\"
+.Dd February 23, 2013
+.Dt CK_BITMAP_UNION 3
+.Sh NAME
+.Nm ck_bitmap_union
+.Nd generates union of two bitmaps
+.Sh LIBRARY
+Concurrency Kit (libck, \-lck)
+.Sh SYNOPSIS
+.In ck_bitmap.h
+.Ft void
+.Fn ck_bitmap_union "ck_bitmap_t *dst" "ck_bitmap_t *src"
+.Sh DESCRIPTION
+The
+.Fn ck_bitmap_union
+function sets all bits in the bitmap pointed to by
+.Fa src
+in the bitmap pointed to by
+.Fa dst .
+.Sh RETURN VALUES
+This function has no return value.
+.Sh SEE ALSO
+.Xr ck_bitmap_base 3 ,
+.Xr ck_bitmap_size 3 ,
+.Xr ck_bitmap_init 3 ,
+.Xr ck_bitmap_reset 3 ,
+.Xr ck_bitmap_set 3 ,
+.Xr ck_bitmap_clear 3 ,
+.Xr ck_bitmap_test 3 ,
+.Xr ck_bitmap_bits 3 ,
+.Xr ck_bitmap_buffer 3
+.Pp
+Additional information available at http://concurrencykit.org/