Inclusion Criteria:  currently homeless, defined as lacking a fixed, regular, and adequate nighttime residence. report any of the following past-month frequencies of substance use (NIDA ASSIST screen) used in prior EMA studies: a) heavy episodic or "binge" drinking (≥4 drinks per day for women/≥5 drinks for men) ≥2 days per month ; b) marijuana use ≥2 days per week; or c) any illicit drug use.  Exclusion Criteria:  -