It specialized in application software for printing, graphics, law enforcement, artificial intelligence, and in implementations of programming languages.

Harlequin employees sometimes referred to themselves as "The 'Late Binding' company" and the firm eventually evolved into a think tank for advanced technologies.

Harlequin had two main lines of business: Other products included data analysis tools created using LispWorks, the Lisp IDE.

MPS was designed to support: In January 2005 employees founded the independently owned LispWorks Limited[3] to focus on the Lisp business.

[14] The firm continues to sell investigation and analysis tools developed by Harlequin originally (such as Link Explorer[15] and Powercase[16]) to a worldwide market.