Swiss voters are deciding whether to grant new powers to their intelligence services such as tracking internet activity, snooping on email and tapping phones in order to tackle spies, criminal hackers and violent extremists.
A new intelligence law, plus pension reforms and environmental policy, are the three issues being considered in Sunday's referendum.
Proponents say the law, passed a year ago but not enacted, is needed to help Switzerland to catch up with other countries who have stronger legal arsenals to counter cyber-crime, snooping or extremist attacks.
Opponents fear it will deplete civil liberties, do little to impede terrorism and chip away at Switzerland's long-vaunted neutrality.
Swiss law currently bars authorities from using anything more than publicly available information or tips from foreign officials when monitoring threats inside Switzerland.