At long last, and after a great deal of wrangling, EN ISO 13849-1 is harmonised to the Machinery Directive by virtue of its listing in the Official Journal of the European Union published on 8 May 2007.
This means that meeting the requirements of EN ISO 13849-1:2006 (Safety of machinery - Safety-related parts of control systems - Part 1: General principles for design) is therefore now an acceptable way by which machine builders can show compliance with the Essential Health and Safety Requirements (EHSRs) of the Machinery Directive (98/37/EC).
The standard that is being replaced, namely EN 954-1:1996, may still be used until 30 November 2009, though EN ISO 13849-1 or another standard - such as EN IEC 62061 - may actually be more appropriate in certain circumstances.
[See this more recent announcement confirming the extended transition period for EN 954-1 - Ed]