diff --git a/icu4c/source/data/cldr-icu-readme.txt b/icu4c/source/data/cldr-icu-readme.txt
index 3b5ab5ffae9..1793cd8cadf 100644
--- a/icu4c/source/data/cldr-icu-readme.txt
+++ b/icu4c/source/data/cldr-icu-readme.txt
@@ -7,6 +7,9 @@
 #    - CLDR (the source of most of the data, and some Java tools)
 #    - ICU4J  (used by the conversion tools)
 #    - ICU4C  (the destination for the new data, and the source for some of it)
+#             (Either check out ICU4C from Subversion, or download the additional 
+#              icu4c-*-data.zip file so that the icu/source/data/ directory is fully
+#              populated.)
 #
 # For an official CLDR data integration into ICU, these should be clean, freshly
 # checked-out. For released CLDR sources, an alternative to checking out sources
diff --git a/icu4c/source/data/icu4j-readme.txt b/icu4c/source/data/icu4j-readme.txt
index ae5b7496409..ad4805c5400 100644
--- a/icu4c/source/data/icu4j-readme.txt
+++ b/icu4c/source/data/icu4j-readme.txt
@@ -21,6 +21,7 @@ In the following,
 	(Windows: build as x86, Release otherwise you will have to set 'CFG' differently below.)
 
 	*NOTE* You should do a full rebuild after any data changes.
+1a.  If you didn't download from Subversion, you will also need the "icu4c-*-data.zip" file.  Unpack this file and replace the icu/source/data directory's contents with the contents of the data directory from the zip file.  
 
 
 2. Step 2 depends on whether you are on a Windows or a Unix-type
@@ -39,9 +40,10 @@ platform.
 *Linux*
 
         $icu4c_build is the ICU4C root build directory,
-        which is $icu4c_root/source in an in-source build
+        which is $icu4c_root/source in an in-source build.
+        (in other words, $icu4c_build is where you ran runConfigureICU or configure)
 
-2c. On the command line, cd to $icu4c_build
+2c. On the command line, cd to $icu4c_build/data
 
 2d. Do
         make JAR=$jdk_bin/jar ICU4J_ROOT=$icu4j_root icu4j-data-install