diff --git a/mps/code/config.h b/mps/code/config.h
index 07531878614..2f753eb1e11 100644
--- a/mps/code/config.h
+++ b/mps/code/config.h
@@ -32,13 +32,13 @@
 #if defined(CONFIG_VAR_WI) || defined(CONFIG_VAR_WE) /* White-hot varieties */
 /* no asserts */
 /* ... so CHECKLEVEL_INITIAL is irrelevant */
-/* no debug diagnostic statistic meters */
+/* no debug statistic meters */
 /* no telemetry log events */
 
 #elif defined(CONFIG_VAR_HI) || defined(CONFIG_VAR_HE) /* Hot varieties */
 #define CONFIG_ASSERT
 #define CHECKLEVEL_INITIAL CheckLevelMINIMAL
-/* no debug diagnostic statistic meters */
+/* no debug statistic meters */
 /* no telemetry log events */
 
 #elif defined(CONFIG_VAR_DI) /* Diagnostic variety */
@@ -69,7 +69,7 @@
 #elif defined(CONFIG_VAR_II)    /* Ice, Internal; variety.ii (HotLog) */
 #define CONFIG_ASSERT
 #define CHECKLEVEL_INITIAL CheckLevelMINIMAL
-/* no debug diagnostic statistic meters */
+/* no debug statistic meters */
 #define CONFIG_LOG
 #endif
 
@@ -89,12 +89,17 @@
 
 
 #if defined(CONFIG_DEBUG)
-/* DEBUG = DIAGNOSTICS = STATISTICs = METERs */
-/* WARNING: this changes the size and fields of MPS structs */
-#define DIAGNOSTICS
+/* CONFIG_DEBUG = STATISTICS = METERs */
+/* Note: the STATISTICS define used to be called "DIAGNOSTICS" (even */
+/* though it controls the STATISTIC system), but the term */
+/* "diagnostic" means something else now: see design/diag/. */
+/* RHSK 2007-06-28 */
+/* WARNING: this may change the size and fields of MPS structs */
+/* (...but see STATISTIC_DECL, which is invariant) */
+#define STATISTICS
 #define MPS_DEBUG_STRING "debug"
 #else
-#define DIAGNOSTICS_NONE
+#define STATISTICS_NONE
 #define MPS_DEBUG_STRING "nondebug"
 #endif
 
diff --git a/mps/code/meter.h b/mps/code/meter.h
index 3e8902a6497..6912ca7afc0 100644
--- a/mps/code/meter.h
+++ b/mps/code/meter.h
@@ -44,12 +44,12 @@ extern void MeterEmit(Meter meter);
 /* Hack: owner is typically only used for MeterInit */
 #define METER_ACC(meter, delta) \
   STATISTIC(MeterAccumulate(&(meter), delta))
-#if defined(DIAGNOSTICS)
+#if defined(STATISTICS)
 #define METER_WRITE(meter, stream) MeterWrite(&(meter), stream)
-#elif defined(DIAGNOSTICS_NONE)
+#elif defined(STATISTICS_NONE)
 #define METER_WRITE(meter, stream) (ResOK)
 #else
-#error "Diagnostics not configured."
+#error "No statistics configured."
 #endif
 #define METER_EMIT(meter) STATISTIC(MeterEmit(meter))
 
diff --git a/mps/code/mpm.h b/mps/code/mpm.h
index 404d0bac54a..44b045b0c1d 100644
--- a/mps/code/mpm.h
+++ b/mps/code/mpm.h
@@ -911,7 +911,7 @@ extern Size VMMapped(VM vm);
 extern void StackProbe(Size depth);
 
 
-/* STATISTIC -- gather diagnostics (in some varieties)
+/* STATISTIC -- gather statistics (in some varieties)
  *
  * The argument of STATISTIC is an expression; the expansion followed by
  * a semicolon is syntactically a statement.
@@ -920,7 +920,7 @@ extern void StackProbe(Size depth);
  * a semicolon is syntactically a statement.
  *
  * STATISTIC_WRITE is inserted in WriteF arguments to output the values
- * of diagnostic fields.
+ * of statistic fields.
  *
  * .statistic.whitehot: The implementation of STATISTIC for
  * non-statistical varieties passes the parameter to DISCARD to ensure
@@ -928,13 +928,13 @@ extern void StackProbe(Size depth);
  * passed as part of a comma-expression so that its type is not
  * important.  This permits an expression of type void.  */
 
-#if defined(DIAGNOSTICS)
+#if defined(STATISTICS)
 
 #define STATISTIC(gather) BEGIN (gather); END
 #define STATISTIC_STAT(gather) BEGIN gather; END
 #define STATISTIC_WRITE(format, arg) (format), (arg),
 
-#elif defined(DIAGNOSTICS_NONE)
+#elif defined(STATISTICS_NONE)
 
 #define STATISTIC(gather) DISCARD(((gather), 0))
 #define STATISTIC_STAT(gather) DISCARD_STAT(gather)
@@ -942,7 +942,7 @@ extern void StackProbe(Size depth);
 
 #else
 
-#error "No diagnostics configured."
+#error "No statistics configured."
 
 #endif
 
diff --git a/mps/code/mpmtypes.h b/mps/code/mpmtypes.h
index f7da1f58d7c..868bfa283ae 100644
--- a/mps/code/mpmtypes.h
+++ b/mps/code/mpmtypes.h
@@ -454,12 +454,12 @@ typedef double WriteFD;
  * leave them in, see design.mps.metrics.
  */
 
-#if defined(DIAGNOSTICS)
+#if defined(STATISTICS)
 #define STATISTIC_DECL(field) field
-#elif defined(DIAGNOSTICS_NONE)
+#elif defined(STATISTICS_NONE)
 #define STATISTIC_DECL(field) field
 #else
-#error "No diagnostics configured."
+#error "No statistics configured."
 #endif