diff --git a/psycopg/connection.h b/psycopg/connection.h
index 33ad30b9..32aaddfc 100644
--- a/psycopg/connection.h
+++ b/psycopg/connection.h
@@ -48,9 +48,6 @@ extern "C" {
 #define CONN_STATUS_SEND_CLIENT_ENCODING       8
 #define CONN_STATUS_SENT_CLIENT_ENCODING       9
 #define CONN_STATUS_GET_CLIENT_ENCODING        10
-#define CONN_STATUS_SEND_TRANSACTION_ISOLATION 11
-#define CONN_STATUS_SENT_TRANSACTION_ISOLATION 12
-#define CONN_STATUS_GET_TRANSACTION_ISOLATION  13
 
 /* async query execution status */
 #define ASYNC_READ  1
diff --git a/psycopg/connection_int.c b/psycopg/connection_int.c
index 4646eea5..0fce84d6 100644
--- a/psycopg/connection_int.c
+++ b/psycopg/connection_int.c
@@ -404,11 +404,6 @@ conn_poll_send(connectionObject *self)
         query = psyco_client_encoding;
         next_status = CONN_STATUS_SENT_CLIENT_ENCODING;
         break;
-    case CONN_STATUS_SEND_TRANSACTION_ISOLATION:
-        /* get the default isolevel */
-        query = psyco_transaction_isolation;
-        next_status = CONN_STATUS_SENT_TRANSACTION_ISOLATION;
-        break;
     default:
         /* unexpected state, error out */
         PyErr_Format(OperationalError,
@@ -444,9 +439,6 @@ conn_poll_send(connectionObject *self)
         case CONN_STATUS_SENT_CLIENT_ENCODING:
             next_status = CONN_STATUS_GET_CLIENT_ENCODING;
             break;
-        case CONN_STATUS_SENT_TRANSACTION_ISOLATION:
-            next_status = CONN_STATUS_GET_TRANSACTION_ISOLATION;
-            break;
         }
     }
     else {
@@ -526,17 +518,17 @@ conn_poll_fetch(connectionObject *self)
             return NULL;
         }
         Dprintf("conn_poll_fetch: got client_encoding %s", self->encoding);
-        next_status = CONN_STATUS_SEND_TRANSACTION_ISOLATION;
-    }
-    else if (self->status == CONN_STATUS_GET_TRANSACTION_ISOLATION) {
-        /* got the default isolevel */
-        self->isolation_level = conn_get_isolation_level(pgres);
-        Dprintf("conn_poll_fetch: got isolevel %ld", self->isolation_level);
 
         /* since this is the last step, set the other instance variables now */
         self->equote = conn_get_standard_conforming_strings(self->pgconn);
         self->protocol = conn_get_protocol_version(self->pgconn);
         self->server_version = (int) PQserverVersion(self->pgconn);
+        /*
+         * asynchronous connections always use isolation level 0, the user is
+         * expected to manage the transactions himself, by sending
+         * (asynchronously) BEGIN and COMMIT statements.
+         */
+        self->isolation_level = 0;
 
         Py_BEGIN_ALLOW_THREADS;
         pthread_mutex_lock(&(self->lock));
diff --git a/psycopg/connection_type.c b/psycopg/connection_type.c
index 3d5629d0..a4f54300 100644
--- a/psycopg/connection_type.c
+++ b/psycopg/connection_type.c
@@ -421,14 +421,12 @@ psyco_conn_poll(connectionObject *self)
 
     case CONN_STATUS_SEND_DATESTYLE:
     case CONN_STATUS_SEND_CLIENT_ENCODING:
-    case CONN_STATUS_SEND_TRANSACTION_ISOLATION:
         /* these mean that we need to wait for the socket to become writable
            to send the rest of our query */
         return conn_poll_send(self);
 
     case CONN_STATUS_GET_DATESTYLE:
     case CONN_STATUS_GET_CLIENT_ENCODING:
-    case CONN_STATUS_GET_TRANSACTION_ISOLATION:
         /* these mean that we are waiting for the results of the queries */
         return conn_poll_fetch(self);