In 1994, new concepts (extensibility, Object Classes, Types parameterization, …) have been introduced in the ASN.1 notation resulting in the publication of four new standards :

- ITU-T X.680 (1994) | ISO/IEC 8824-1:1995, Specification of Basic Notation

- ITU-T X.681 (1994) | ISO/IEC 8824-2:1995, Information Object Specification

- ITU-T X.682 (1994) | ISO/IEC 8824-3:1995, Constraint Specification

- ITU-T X.683 (1994) | ISO/IEC 8824-4:1995, Parameterization of ASN.1 Specifications

New encoding rules, named PER (Packed Encoding Rules), have also been specified resulting in the publication of two new standards:

- ITU-T X.690 (1994) | ISO/IEC 8825-1:1995, Specification of Basic Encoding Rules (BER),Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)

- ITU-T X.691 (1994) | ISO/IEC 8825-2:1995, Specification of Packed Encoding Rules (PER)

This version of the ASN.1 standards is commonly called ASN.1:1994.

In 1999, a new release of the ASN.1 standards has been published. Modifications are mainly editorial and consist in integrating amendments and technical corrigendum issued since the ASN.1: 1994 release. This version is commonly called ASN.1: 1997.