Whitney Houston is back in rehab.  

A spokesperson for the singer confirms that she has voluntarily entered "an out-patient program for drug and alcohol treatment."  

Houston looked bloated and disheveled last Thursday in Los Angeles where she performed onstage with Chaka Khan at a Prince concert.

It's the latest setback for the 47-year-old star, who has long struggled with substance abuse.  

Last year, Houston's comeback tour was plagued with problems. She canceled dates due to illness and audience members complained her voice was raspy.

Now she is reportedly "cleansing herself" before beginning to work on a new movie, a sequel to her 1995 hit movie Waiting to Exhale.