Police are treating the death of a 60-year-old man as suspicious.
Officers from Sussex Police were called to a flat in Durrington Gardens, The Causeway, Goring-by-Sea at 8.24pm yesterday.
A 60-year-old man was discovered, slumped on a sofa, being attended to by paramedics for a uspected heroin overdose.
They were unable to revive him and he was pronounced dead at 8.40pm.
A 27-year-old woman, who was in the flat at the time, was arrested on suspicion of being concerned in the supply of Class A drugs and is in custody awaiting interview.
A police forensics team is in place at the moment.
Police say a post mortem examination will be held to find out how the man died and the coroner has been informed.
Detective Inspector Dave Wardley Wilkins, of the Sussex Police priority crime team, said: "This is one of three deaths in West Sussex in as many days, all of which are believed to have involved drugs.
"There is no reason to link them at this stage, but it is clearly something we are mindful of as we await the results of post mortem examinations and forensic tests in each case."
He added: "Drugs can have a devastating effect on the lives of individual drug users, their families and the wider community. Any drugs-related death means a personal and tragic loss of life for that person's loved ones, and this should never be forgotten."
Police warn that illicit drugs are always fraught with danger, with purity and adulteration both key issues, and anyone using them may put themselves at risk.
Anyone who has any information on the supply or selling of illegal drugs is urged phone Sussex Police on 101 or email firstname.lastname@example.org to pass on details.
Alternatively they can speak to any police officer or their local Police Community Support Officer, or if they prefer, contact the independent charity Crimestoppers free and anonymously on 0800 555 111.