Four men and seven women have been arrested over offences relating to animal rights extremist activities.
West Mercia Police carried out a planned operation during Tuesday and Wednesday involving 120 officers and other national police agencies.
Arrests were made in Gloucestershire, Herefordshire, Worcestershire, the West Midlands and Shropshire.
Items including computers were seized during searches under the Serious Organised Crime and Police Act 2005.
Police said the arrests were not in connection with letters sent to shareholders of GlaxoSmithKline or Darley Oaks guinea pig farm in Staffordshire, which closed after a six-year campaign by animal rights protestors.
All those arrested - aged between 20 and 60 - have been released on bail to appear at police stations in the West Mercia area in May and June.