Index: lang.opt
===================================================================
--- lang.opt	(revision 127224)
+++ lang.opt	(working copy)
@@ -212,6 +212,10 @@ fmax-stack-var-size=
 Fortran RejectNegative Joined UInteger
 -fmax-stack-var-size=<n>	Size in bytes of the largest array that will be put on the stack
 
+fmodule-private
+Fortran
+Set default accessibility of module entities to PRIVATE.
+
 fopenmp
 Fortran
 Enable OpenMP
Index: gfortran.h
===================================================================
--- gfortran.h	(revision 127224)
+++ gfortran.h	(working copy)
@@ -1865,6 +1865,7 @@ typedef struct
   int flag_d_lines;
   int flag_openmp;
   int flag_sign_zero;
+  int flag_module_private;
 
   int fpe;
 
Index: invoke.texi
===================================================================
--- invoke.texi	(revision 127228)
+++ invoke.texi	(working copy)
@@ -121,7 +121,7 @@ by type.  Explanations are in the follow
 -ffixed-line-length-@var{n}  -ffixed-line-length-none @gol
 -ffree-line-length-@var{n}  -ffree-line-length-none @gol
 -fdefault-double-8  -fdefault-integer-8  -fdefault-real-8 @gol
--fcray-pointer  -fopenmp  -frange-check -fno-backslash }
+-fcray-pointer  -fopenmp  -frange-check -fno-backslash -fmodule-private}
 
 @item Error and Warning Options
 @xref{Error and Warning Options,,Options to request or suppress errors
@@ -238,6 +238,14 @@ Allow @samp{$} as a valid character in a
 Change the interpretation of backslashes in string literals from
 ``C-style'' escape characters to a single backslash character.
 
+@item -fmodule-private
+@opindex @code{fmodule-private}
+@cindex module entities
+@cindex private
+Set the default accessibility of module entities to @code{PRIVATE}.
+Use-associated entities will not be accessible unless they are explicitly
+declared as @code{PUBLIC}.
+
 @item -ffixed-line-length-@var{n}
 @opindex @code{ffixed-line-length-}@var{n}
 @cindex file format, fixed
Index: module.c
===================================================================
--- module.c	(revision 127224)
+++ module.c	(working copy)
@@ -3714,7 +3714,10 @@ gfc_check_access (gfc_access specific_ac
   if (specific_access == ACCESS_PRIVATE)
     return FALSE;
 
-  return default_access != ACCESS_PRIVATE;
+  if (gfc_option.flag_module_private)
+    return default_access == ACCESS_PUBLIC;
+  else
+    return default_access != ACCESS_PRIVATE;
 }
 
 
Index: options.c
===================================================================
--- options.c	(revision 127224)
+++ options.c	(working copy)
@@ -93,6 +93,7 @@ gfc_init_options (unsigned int argc ATTR
   gfc_option.flag_preprocessed = 0;
   gfc_option.flag_automatic = 1;
   gfc_option.flag_backslash = 1;
+  gfc_option.flag_module_private = 0;
   gfc_option.flag_backtrace = 0;
   gfc_option.flag_allow_leading_underscore = 0;
   gfc_option.flag_dump_core = 0;
@@ -575,6 +576,10 @@ gfc_handle_option (size_t scode, const c
       gfc_option.flag_max_stack_var_size = value;
       break;
 
+    case OPT_fmodule_private:
+      gfc_option.flag_module_private = value;
+      break;
+      
     case OPT_frange_check:
       gfc_option.flag_range_check = value;
       break;
Index: gcc/testsuite/gfortran.dg/module_private_1.f90
===================================================================
--- gcc/testsuite/gfortran.dg/module_private_1.f90	(revision 0)
+++ gcc/testsuite/gfortran.dg/module_private_1.f90	(revision 0)
@@ -0,0 +1,20 @@
+! { dg-do compile }
+! { dg-options "-fmodule-private" }
+module bar
+  implicit none
+  public :: i
+  integer :: i
+end module bar
+
+module foo
+  implicit none
+  integer :: j
+end module foo
+
+program main
+  use bar, only : i
+  use foo, only : j ! { dg-error "not found in module" }
+  i = 1
+  j = 1
+  print *, i, j
+end program main