diff --git a/lib/libc/stdlib/strtod.3 b/lib/libc/stdlib/strtod.3
index 5a9b3628a99e..cc7cad9a33b8 100644
--- a/lib/libc/stdlib/strtod.3
+++ b/lib/libc/stdlib/strtod.3
@@ -1,4 +1,4 @@
-.\"	$NetBSD: strtod.3,v 1.10 2001/09/16 01:31:53 wiz Exp $
+.\"	$NetBSD: strtod.3,v 1.11 2002/01/28 00:10:04 kleink Exp $
 .\"
 .\" Copyright (c) 1990, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -37,7 +37,7 @@
 .\"
 .\"     from: @(#)strtod.3	8.1 (Berkeley) 6/4/93
 .\"
-.Dd March 21, 2001
+.Dd January 28, 2002
 .Dt STRTOD 3
 .Os
 .Sh NAME
@@ -62,10 +62,27 @@ to
 representation.
 .Pp
 The expected form of the string is an optional plus (``+'') or minus
-sign (``\-'') followed by a sequence of digits optionally containing
+sign (``\-'') followed by one of the following:
+.Bl -dash
+.It
+a sequence of digits optionally containing
 a decimal-point character, optionally followed by an exponent.
 An exponent consists of an ``E'' or ``e'', followed by an optional plus
 or minus sign, followed by a sequence of digits.
+.It
+one of
+.Li INF
+or
+.Li INFINITY ,
+ignoring case.
+.It
+one of
+.Li NAN
+or
+.Li NAN(n-char-sequence-opt) ,
+ignoring case.
+This implementation currently does not interpret such a sequence.
+.El
 .Pp
 Leading white-space characters in the string (as defined by the
 .Xr isspace 3
@@ -75,6 +92,24 @@ The
 .Fn strtod
 function returns the converted value, if any.
 .Pp
+A character sequence
+.Li INF
+or
+.Li INFINITY
+is converted to \*(If,
+if supported, else to the largest finite floating-point number representable
+on the machine (i.e.,
+.Tn VAX Ns ).
+.Pp
+A character sequence
+.Li NAN
+or
+.Li NAN(n-char-sequence-opt)
+is converted to a quiet \*(Na, if supported, else to a
+.Dq reserved operand
+for that machine (i.e.,
+.Tn VAX Ns ).
+.Pp
 If
 .Fa endptr
 is not
@@ -108,6 +143,7 @@ Overflow or underflow occurred.
 .Xr atof 3 ,
 .Xr atoi 3 ,
 .Xr atol 3 ,
+.Xr math 3 ,
 .Xr strtol 3 ,
 .Xr strtoul 3
 .Sh STANDARDS
diff --git a/lib/libc/stdlib/strtod.c b/lib/libc/stdlib/strtod.c
index d90a7f73562c..2238dae84f48 100644
--- a/lib/libc/stdlib/strtod.c
+++ b/lib/libc/stdlib/strtod.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: strtod.c,v 1.38 2001/12/15 03:39:53 thorpej Exp $	*/
+/*	$NetBSD: strtod.c,v 1.39 2002/01/28 00:10:04 kleink Exp $	*/
 
 /****************************************************************
  *
@@ -93,7 +93,7 @@
 
 #include <sys/cdefs.h>
 #if defined(LIBC_SCCS) && !defined(lint)
-__RCSID("$NetBSD: strtod.c,v 1.38 2001/12/15 03:39:53 thorpej Exp $");
+__RCSID("$NetBSD: strtod.c,v 1.39 2002/01/28 00:10:04 kleink Exp $");
 #endif /* LIBC_SCCS and not lint */
 
 #define Unsigned_Shifts
@@ -1282,6 +1282,46 @@ strtod
 		goto ret;
 	}
 
+	/* "INF" or "INFINITY" */
+	if (tolower(*s) == 'i' && strncasecmp(s, "inf", 3) == 0) {
+		if (strncasecmp(s + 3, "inity", 5) == 0)
+			s += 8;
+		else
+			s += 3;
+
+		value(rv) = HUGE_VAL;
+		goto ret;
+	}
+
+	/* "NAN" or "NAN(n-char-sequence-opt)" */
+	if (tolower(*s) == 'n' && strncasecmp(s, "nan", 3) == 0) {
+#ifdef IEEE_Arith
+		/* Build a quiet NaN. */
+		word0(rv) = Exp_mask | ((1 << Exp_shift) - 1);
+		word1(rv) = 0;
+#else
+#ifdef VAX
+		/* Lacking a quiet NaN, build a reserved operand. */
+		word0(rv) = Sign_bit;
+		word1(rv) = 0;
+#endif
+#endif
+		s+= 3;
+
+		/* Don't interpret (n-char-sequence-opt), for now. */
+		if (*s == '(') {
+			s0 = s;
+			for (s++; *s != ')' && *s != '\0'; s++)
+				;
+			if (*s == ')')
+				s++;	/* Skip over closing paren ... */
+			else
+				s = s0;	/* ... otherwise go back. */
+		}
+
+		goto ret;
+	}
+
 	if (*s == '0') {
 		nz0 = 1;
 		while(*++s == '0') ;