diff --git a/sumdb/server.go b/sumdb/server.go
index 1e1779d..216a256 100644
--- a/sumdb/server.go
+++ b/sumdb/server.go
@@ -6,6 +6,7 @@
 package sumdb
 
 import (
+	"bytes"
 	"context"
 	"net/http"
 	"os"
@@ -150,6 +151,8 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 					http.Error(w, err.Error(), http.StatusInternalServerError)
 					return
 				}
+				// Data tiles contain formatted records without the first line with record ID.
+				_, msg, _ = bytes.Cut(msg, []byte{'\n'})
 				data = append(data, msg...)
 			}
 			w.Header().Set("Content-Type", "text/plain; charset=UTF-8")
diff --git a/sumdb/tlog/note.go b/sumdb/tlog/note.go
index ce5353e..fc6d5fa 100644
--- a/sumdb/tlog/note.go
+++ b/sumdb/tlog/note.go
@@ -73,13 +73,16 @@ func ParseTree(text []byte) (tree Tree, err error) {
 var errMalformedRecord = errors.New("malformed record data")
 
 // FormatRecord formats a record for serving to a client
-// in a lookup response or data tile.
+// in a lookup response.
 //
 // The encoded form is the record ID as a single number,
 // then the text of the record, and then a terminating blank line.
 // Record text must be valid UTF-8 and must not contain any ASCII control
 // characters (those below U+0020) other than newline (U+000A).
 // It must end in a terminating newline and not contain any blank lines.
+//
+// Responses to data tiles consist of concatenated formatted records from each of
+// which the first line, with the record ID, is removed.
 func FormatRecord(id int64, text []byte) (msg []byte, err error) {
 	if !isValidRecordText(text) {
 		return nil, errMalformedRecord