diff --git a/doc/fix_box_relax.html b/doc/fix_box_relax.html
index cf8bee4f745fd33a6a9201847bc33ed576203c98..1486e17651bb8c0000320847b8f50c2c9f1f753f 100644
--- a/doc/fix_box_relax.html
+++ b/doc/fix_box_relax.html
@@ -82,6 +82,19 @@ re-scaled.  This can be useful for leaving the coordinates of atoms in
 a solid substrate unchanged and controlling the pressure of a
 surrounding fluid.
 </P>
+<P>IMPORTANT NOTE: Appling an external pressure to tilt dimensions <I>xy</I>,
+<I>xz</I>, <I>yz</I> can sometimes result in arbitrarily large values of the
+tilt dimensions, i.e. a dramatically deformed simulation box.  This
+typically indicates that there is something badly wrong with how the
+simulation was constructed.  The two most common sources of this error
+are applying a shear stress to a liquid system or specifying an
+external shear stress tensor that exceeds the yield stress of the
+solid.  In either case the minimization is either not going to
+converge at all, or converge to a bogus conformation.  Note that
+LAMMPS will not throw an error when the tilt value becomes extreme,
+but the final box may be unsuitable for running dynamics on, unless
+fix deform is used first to remap the box to a valid tilt value.
+</P>
 <HR>
 
 <P>The <I>couple</I> keyword allows two or three of the diagonal components of
diff --git a/doc/fix_box_relax.txt b/doc/fix_box_relax.txt
index 606cb3edab25e223183973a92cdca05621fd2dc9..510458504cc07e827ed85bc64bc653060325cf5a 100644
--- a/doc/fix_box_relax.txt
+++ b/doc/fix_box_relax.txt
@@ -76,6 +76,19 @@ re-scaled.  This can be useful for leaving the coordinates of atoms in
 a solid substrate unchanged and controlling the pressure of a
 surrounding fluid.
 
+IMPORTANT NOTE: Appling an external pressure to tilt dimensions {xy},
+{xz}, {yz} can sometimes result in arbitrarily large values of the
+tilt dimensions, i.e. a dramatically deformed simulation box.  This
+typically indicates that there is something badly wrong with how the
+simulation was constructed.  The two most common sources of this error
+are applying a shear stress to a liquid system or specifying an
+external shear stress tensor that exceeds the yield stress of the
+solid.  In either case the minimization is either not going to
+converge at all, or converge to a bogus conformation.  Note that
+LAMMPS will not throw an error when the tilt value becomes extreme,
+but the final box may be unsuitable for running dynamics on, unless
+fix deform is used first to remap the box to a valid tilt value.
+
 :line
 
 The {couple} keyword allows two or three of the diagonal components of