AIMS: We tested whether patrons of the night-economy who had co-consumed energy drinks or illicit stimulants with alcohol had higher blood alcohol concentration (BAC) levels than patrons who had consumed only alcohol. DESIGN: Street intercept surveys (n=4227) were undertaken between 9pm-5am over a period of seven months. SETTING: Interviews were undertaken with patrons walking through entertainment precincts, queuing to enter venues, or exiting venues, in five Australian cities. PARTICIPANTS: The response rate was 92.1%; more than half of the study sample was male (60.2%) and the median age was 23 years (range 18-72). MEASUREMENTS: Data were collected on demographics, length of drinking session, venue types visited, types and quantity of alcohol consumed and other substance use. A BAC reading was recorded and a sub-sample of participants were tested for other drug use. FINDINGS: Compared to alcohol-only consumers (0.068%), illicit stimulant consumers (0.080%; p=.004) and energy drink consumers (0.074%; pCONCLUSIONS: While stimulant use does not predict BAC in and of itself, stimulants users are more likely to engage in prolonged sessions of heavy alcohol consumption and a range of risk-taking behaviours on a night out, which may explain higher levels of BAC among stimulants users, at least in the initial stages of the drinking session. Language: en