diff --git a/sa/database.go b/sa/database.go
index 98f722eaa..214c2215d 100644
--- a/sa/database.go
+++ b/sa/database.go
@@ -264,8 +264,6 @@ func initTables(dbMap *gorp.DbMap) {
 	regTable.SetVersionCol("LockCol")
 	regTable.ColMap("Key").SetNotNull(true)
 	regTable.ColMap("KeySHA256").SetNotNull(true).SetUnique(true)
-	dbMap.AddTableWithName(authzModel{}, "authz").SetKeys(false, "ID")
-	dbMap.AddTableWithName(challModel{}, "challenges").SetKeys(true, "ID")
 	dbMap.AddTableWithName(issuedNameModel{}, "issuedNames").SetKeys(true, "ID")
 	dbMap.AddTableWithName(core.Certificate{}, "certificates").SetKeys(true, "ID")
 	dbMap.AddTableWithName(core.CertificateStatus{}, "certificateStatus").SetKeys(true, "ID")
diff --git a/sa/model.go b/sa/model.go
index 577fded83..7062942b4 100644
--- a/sa/model.go
+++ b/sa/model.go
@@ -225,25 +225,6 @@ type regModel struct {
 	Status    string `db:"status"`
 }
 
-// challModel is the description of a core.Challenge in the database
-//
-// The Validation field is a stub; the column is only there for backward compatibility.
-type challModel struct {
-	ID              int64  `db:"id"`
-	AuthorizationID string `db:"authorizationID"`
-
-	Type             core.AcmeChallenge `db:"type"`
-	Status           core.AcmeStatus    `db:"status"`
-	Error            []byte             `db:"error"`
-	Token            string             `db:"token"`
-	KeyAuthorization string             `db:"keyAuthorization"`
-	ValidationRecord []byte             `db:"validationRecord"`
-	AttemptedAt      time.Time          `db:"attemptedAt"`
-
-	// TODO(#1818): Remove, this field is unused, but is kept temporarily to avoid a database migration.
-	Validated bool `db:"validated"`
-}
-
 func registrationPbToModel(reg *corepb.Registration) (*regModel, error) {
 	// Even though we don't need to convert from JSON to an in-memory JSONWebKey
 	// for the sake of the `Key` field, we do need to do the conversion in order
@@ -319,39 +300,6 @@ func registrationModelToPb(reg *regModel) (*corepb.Registration, error) {
 	}, nil
 }
 
-func modelToChallenge(cm *challModel) (core.Challenge, error) {
-	c := core.Challenge{
-		Type:                     cm.Type,
-		Status:                   cm.Status,
-		Token:                    cm.Token,
-		ProvidedKeyAuthorization: cm.KeyAuthorization,
-		Validated:                &cm.AttemptedAt,
-	}
-	if len(cm.Error) > 0 {
-		var problem probs.ProblemDetails
-		err := json.Unmarshal(cm.Error, &problem)
-		if err != nil {
-			return core.Challenge{}, badJSONError(
-				"failed to unmarshal challenge model's error",
-				cm.Error,
-				err)
-		}
-		c.Error = &problem
-	}
-	if len(cm.ValidationRecord) > 0 {
-		var vr []core.ValidationRecord
-		err := json.Unmarshal(cm.ValidationRecord, &vr)
-		if err != nil {
-			return core.Challenge{}, badJSONError(
-				"failed to unmarshal challenge model's validation record",
-				cm.ValidationRecord,
-				err)
-		}
-		c.ValidationRecord = vr
-	}
-	return c, nil
-}
-
 type recordedSerialModel struct {
 	ID             int64
 	Serial         string
diff --git a/sa/model_test.go b/sa/model_test.go
index 7395825cc..6453d8c08 100644
--- a/sa/model_test.go
+++ b/sa/model_test.go
@@ -146,40 +146,6 @@ func TestAuthzModel(t *testing.T) {
 	test.AssertError(t, err, "authzPBToModel didn't fail with multiple non-pending challenges")
 }
 
-// TestModelToChallengeBadJSON tests that converting a challenge model with an
-// invalid validation error field or validation record field produces the
-// expected bad JSON error.
-func TestModelToChallengeBadJSON(t *testing.T) {
-	badJSON := []byte(`{`)
-
-	testCases := []struct {
-		Name  string
-		Model *challModel
-	}{
-		{
-			Name: "Bad error field",
-			Model: &challModel{
-				Error: badJSON,
-			},
-		},
-		{
-			Name: "Bad validation record field",
-			Model: &challModel{
-				ValidationRecord: badJSON,
-			},
-		},
-	}
-	for _, tc := range testCases {
-		t.Run(tc.Name, func(t *testing.T) {
-			_, err := modelToChallenge(tc.Model)
-			test.AssertError(t, err, "expected error from modelToChallenge")
-			var badJSONErr errBadJSON
-			test.AssertErrorWraps(t, err, &badJSONErr)
-			test.AssertEquals(t, string(badJSONErr.json), string(badJSON))
-		})
-	}
-}
-
 // TestModelToOrderBADJSON tests that converting an order model with an invalid
 // validation error JSON field to an Order produces the expected bad JSON error.
 func TestModelToOrderBadJSON(t *testing.T) {