From Traderpedia

Definition: A collaboration between the TSX, MX, Vancouver and Alberta Stock Exchanges.

Established in 1999, it was to focus on so-called 'junior' companies.

The definition of 'junior' in this case were companies that were too small to be listed on the TSX.

In 2001, the CDNX was acquired by TSX, and became known as the TSX Venture Exchange.