Written by Felix Cavaliere and Eddie Brigati, and originally recorded by The Young Rascals for their 1967 album Groovin' with a single release in August 1967 affording the group their fourth Top 10 hit peaking at No. 4. Cavaliere has stated: "The only reason we were brave enough to do that was [because] the Beatles did 'Michelle' and 'Yesterday'." (Cavaliere had an especial awareness of the Beatles having toured Europe with them in 1963 when Cavaliere was a member of Joey Dee and the Starliters; also the Rascals would open for the Beatles at Shea Stadium 15 August 1965). The track features the sounds of a trumpet, bass, piano, drums, and strings, giving the feeling of cabaret music as well as a concertina, chosen to add the feel of a French café. "How Can I Be Sure" was one of several songs inspired by group founder Felix Cavaliere's girlfriend Adrienne Becchuri, a Pelham (New York) high school student Cavaliere met in 1966 the year he turned 24: (Felix Cavaliere quote:) "I fell madly in love with this woman who actually turned out to be a muse...[R]eally the only reason she was in my life [was to] spark that kind of emotion and feeling that generates those types of songs." Cavaliere and Buccheri remained a couple for a year, with Cavaliere first celebrating Buccheri in the blissful Rascals' hits "Groovin'" and "A Girl Like You", and then with the introspective "How Can I Be Sure" expressing doubts about the relationship — he and Buccheri had recently become engaged, and despite the positive resolution of the song Cavaliere did in fact decide that he and Buccheri best part ((Felix Cavaliere quote:)I woke up one day and said: 'What the hell am I doing? I’m going out with a kid.'").