Cancer-stricken actress Karen Black is fighting for her life in hospital after she was struck down with pneumonia.

The Easy Rider star, 73, went public with her cancer fight in 2012, revealing she is battling a rare form of the disease which affects the bile duct, and she made an appeal for donations to fund her treatment.

However, Black's husband Stephen Eckelberry has revealed the actress has suffered a major setback and is now in hospital battling a lung infection.

In a series of posts on Black's page, he writes, "Karen has been in the hospital this week for pneumonia, we welcome your prayers. Love, Stephen, Karen's husband."

Black's friend, actress Juliette Lewis, also asked fans to keep the star in their thoughts, adding, "Hi gorgeous souls can u (sic) please say a prayer of eternal love and strength for my glorious mentor Karen Black? Her cancer fight is almost over."