diff --git a/lexer.go b/lexer.go
index 77879dc..d11de42 100644
--- a/lexer.go
+++ b/lexer.go
@@ -204,6 +204,14 @@ func (l *tomlLexer) lexRvalue() tomlLexStateFn {
 			return l.lexFalse
 		}
 
+		if l.follow("inf") {
+			return l.lexInf
+		}
+
+		if l.follow("nan") {
+			return l.lexNan
+		}
+
 		if isSpace(next) {
 			l.skip()
 			continue
@@ -265,6 +273,18 @@ func (l *tomlLexer) lexFalse() tomlLexStateFn {
 	return l.lexRvalue
 }
 
+func (l *tomlLexer) lexInf() tomlLexStateFn {
+	l.fastForward(3)
+	l.emit(tokenInf)
+	return l.lexRvalue
+}
+
+func (l *tomlLexer) lexNan() tomlLexStateFn {
+	l.fastForward(3)
+	l.emit(tokenNan)
+	return l.lexRvalue
+}
+
 func (l *tomlLexer) lexEqual() tomlLexStateFn {
 	l.next()
 	l.emit(tokenEqual)
@@ -651,7 +671,14 @@ func (l *tomlLexer) lexNumber() tomlLexStateFn {
 
 	if r == '+' || r == '-' {
 		l.next()
+		if l.follow("inf") {
+			return l.lexInf
+		}
+		if l.follow("nan") {
+			return l.lexNan
+		}
 	}
+
 	pointSeen := false
 	expSeen := false
 	digitSeen := false
diff --git a/parser.go b/parser.go
index b219bf7..04b1d5c 100644
--- a/parser.go
+++ b/parser.go
@@ -5,6 +5,7 @@ package toml
 import (
 	"errors"
 	"fmt"
+	"math"
 	"reflect"
 	"regexp"
 	"strconv"
@@ -243,6 +244,13 @@ func (p *tomlParser) parseRvalue() interface{} {
 		return true
 	case tokenFalse:
 		return false
+	case tokenInf:
+		if tok.val[0] == '-' {
+			return math.Inf(-1)
+		}
+		return math.Inf(1)
+	case tokenNan:
+		return math.NaN()
 	case tokenInteger:
 		cleanedVal := cleanupNumberToken(tok.val)
 		var err error
diff --git a/parser_test.go b/parser_test.go
index 3818075..90eb0dc 100644
--- a/parser_test.go
+++ b/parser_test.go
@@ -2,6 +2,7 @@ package toml
 
 import (
 	"fmt"
+	"math"
 	"reflect"
 	"testing"
 	"time"
@@ -93,6 +94,25 @@ func TestSimpleNumbers(t *testing.T) {
 	})
 }
 
+func TestSpecialFloats(t *testing.T) {
+	tree, err := Load(`
+normalinf = inf
+plusinf = +inf
+minusinf = -inf
+normalnan = nan
+plusnan = +nan
+minusnan = -nan
+`)
+	assertTree(t, tree, err, map[string]interface{}{
+		"normalinf": math.Inf(1),
+		"plusinf":   math.Inf(1),
+		"minusinf":  math.Inf(-1),
+		"normalnan": math.NaN(),
+		"plusnan":   math.NaN(),
+		"minusnan":  math.NaN(),
+	})
+}
+
 func TestHexIntegers(t *testing.T) {
 	tree, err := Load(`a = 0xDEADBEEF`)
 	assertTree(t, tree, err, map[string]interface{}{"a": int64(3735928559)})
diff --git a/token.go b/token.go
index 5581fe0..1a90813 100644
--- a/token.go
+++ b/token.go
@@ -23,6 +23,8 @@ const (
 	tokenTrue
 	tokenFalse
 	tokenFloat
+	tokenInf
+	tokenNan
 	tokenEqual
 	tokenLeftBracket
 	tokenRightBracket
@@ -55,6 +57,8 @@ var tokenTypeNames = []string{
 	"True",
 	"False",
 	"Float",
+	"Inf",
+	"NaN",
 	"=",
 	"[",
 	"]",
diff --git a/tomltree_write.go b/tomltree_write.go
index f5ef124..d322a97 100644
--- a/tomltree_write.go
+++ b/tomltree_write.go
@@ -54,9 +54,9 @@ func tomlValueStringRepresentation(v interface{}, indent string, arraysOneElemen
 		// Ensure a round float does contain a decimal point. Otherwise feeding
 		// the output back to the parser would convert to an integer.
 		if math.Trunc(value) == value {
-			return strconv.FormatFloat(value, 'f', 1, 32), nil
+			return strings.ToLower(strconv.FormatFloat(value, 'f', 1, 32)), nil
 		}
-		return strconv.FormatFloat(value, 'f', -1, 32), nil
+		return strings.ToLower(strconv.FormatFloat(value, 'f', -1, 32)), nil
 	case string:
 		return "\"" + encodeTomlString(value) + "\"", nil
 	case []byte:
diff --git a/tomltree_write_test.go b/tomltree_write_test.go
index 5ea59bc..206203b 100644
--- a/tomltree_write_test.go
+++ b/tomltree_write_test.go
@@ -309,6 +309,24 @@ func TestTreeWriteToFloat(t *testing.T) {
 	}
 }
 
+func TestTreeWriteToSpecialFloat(t *testing.T) {
+	expected := `a = +inf
+b = -inf
+c = nan`
+
+	tree, err := Load(expected)
+	if err != nil {
+		t.Fatal(err)
+	}
+	str, err := tree.ToTomlString()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.TrimSpace(str) != strings.TrimSpace(expected) {
+		t.Fatalf("Expected:\n%s\nGot:\n%s", expected, str)
+	}
+}
+
 func BenchmarkTreeToTomlString(b *testing.B) {
 	toml, err := Load(sampleHard)
 	if err != nil {