This paper presents some of the specific challenges and opportunities for inkjet in the security printing sector. It follows on from a paper at this conference last year that examined the place of toner based printing. Both papers examine the technical problems that are specific to this market sector and the opportunities that arise from these, particularly in the area of the physics and chemistry of the materials in the digital printing process. In this paper particular emphasis will be given to the challenge inkjet faces in security paper printing as market requirements diverge from typical office based inkjet. This work examines the wetting and penetration of inkjet ink on security printing substrates. Inkjet engines used in this market sector from a number of manufacturers and generations are discussed and results presented. The implications of practical variables such as print driver settings are also included.