Marcaria Smart, 60, also known as Carol Smart, and Segundia Allen, 63, also known as Rita Allen, are known to frequent local casinos, including Cache Creek in Brooks, Napa Valley Casino in American Canyon, San Pablo Lytton Casino and the California Grand Casino in Pacheco, police Lt. Ken Weaver said.
Smart was last seen Wednesday by her husband as she was leaving in her black 1992 Pontiac Grand Am to visit Allen at her Vallejo home, Weaver said.
Police believe both women are in Allen's white 2002 Cadillac Escalade, which has a California license plate number 5SOA770.
Both women are physically and mentally healthy, Weaver said.
Smart is 5 feet 4 inches tall and 135 pounds with brown eyes and blonde hair.
Allen is 5 feet 4 inches tall and 115 pounds with brown eyes and black hair.
Anyone with information about their whereabouts is asked to call detective John Garcia at (707) 648-4517 or detective Mat Mustard at (707) 648-4514.