Ken Loach’s debut feature stars Carol White, the star of his earlier Cathy Come Home and Up the Junction, as a young working-class mother living in London who embarks on a number of tumultuous relationships, often with criminals. Although living in poverty in the slums and mistreated by her lovers, Joy remains resilient about her lot. Unusually for the director, Loach uses techniques that distance the audience from the action, such as Joy’s voiceover and inter-titles more reminiscent of the silent era.  

For the first time he cast a well known star, Terence Stamp (The Collector, Far from the Madding Crowd), although he would continue to use non-professionals in his later work. It’s not one of his greatest critical successes, but Poor Cow shows Loach’s concerns with society’s treatment of the working-class were there from the start of his film career. Scenes from Poor Cow showing Terence Stamp as a young man would be used in the flashback sequences of Steven Soderbergh’s The Limey (1999).
British Film Institute

“Loach’s outstanding gift is a rare one – he has a quite astonishing rapport with actors. He has carried this talent over to the big screen, getting a marvellously warm and likeable portrait from Carol White.”    Sight & Sound, 1967
 
With a montage of seaside shots filmed in Bognor Regis, Ken Loach's debut feature is possibly the ultimate definition of a 'kitchen sink' drama. The subject material is quite grim in places but Carol White's superb performance carries you through.

According to Alexander Walker's 1974 book Hollywood, England, Poor Cow was a surprise success at the box office. 

It sold to the US for more than its production cost and did extremely well in Italy and Britain. Here's an anecdote from Bognor resident  Doug Rollings

Me and three friends were in that film, though we didn't know it till we saw it, 4 rockers walking on the prom.