We describe an 18-month intervention that was designed to improve opportunistic screening for chlamydia in General Practice. Key strategies included engaging and informing general practitioners, adopting a simplified screening protocol, providing feedback on practice testing performance and developing resources for use with patients. This uncontrolled before and after study found that the overall impact on testing was modest and largely transient, and was insufficient to impact on the current chlamydia epidemic. Major additional measures would be required to further substantially increase testing levels. These could include financial incentives linked to screening performance and increased community awareness to increase patient demand for testing.