Background: Spontaneous reports of suspected adverse drug reactions to regulatory bodies and market authorization holders are important in pharmacovigilance. Follow-up information, which can be difficult to obtain, is often required from reporters; therefore, we developed targeted follow-up letters that we hoped would make replying easier. Objective: To examine the effects of introducing targeted letters on responses to follow-up requests from a regional pharmacovigilance centre in the UK. Method: In January 2001 we redesigned our follow-up request letter to include tick-boxes targeted to obtain the appropriate information from reporters. Response rates and the requirement for a second follow-up letter were examined for the 5-year period before introduction of the targeted follow-up letter (1996-2000) and the 5 years after the change to the targeted follow-up system (2001-5). In an 18-month sub-study examining data from 2001-2, time from the production of the first targeted follow-up letter to receipt of a response from reporters was also measured. Results: The introduction of targeted follow-up letters was associated with an increase in the mean annual response rate for follow-up from 36.4% in the 5 years pre-targeted follow-up to 60.5% in the 5 years post-targeted follow-up (p < 0.0001). Fifty percent of all successful follow-up responses were obtained within 70 days. Conclusion: Targeted follow-up letters were associated with increased followup success rates. Results also indicate that closing cases to follow-up information at 70 days would allow collection of 78% of all follow-up that would ever arrive.