OBJECTIVES: The purpose of the present study was to assess the levels of nicotine and cotinine in biological fluids (plasma, saliva, and urine) following hubble-bubble (HB) smoking. METHODS: Fourteen healthy male volunteers, aged 28 +/- 8 years, body weight of 82.7 +/- 13.53 kg, participated in the study. All volunteers were habitual HB smokers for 3.29 +/- 1.90 years who smoked at least 3 runs per week with an average of 20 g Mua'sel per run. Volunteers were requested to avoid smoking, at least 84 hours prior to the time of the study. After baseline samples were taken, volunteers started smoking 20 g of Mua'sel for a period of 45 minutes. Heparinized blood samples (5 or 10 ml each) were drawn for nicotine and cotinine analysis before, during and after the smoking period. Saliva samples were collected just before smoking (time 0) and at the end of smoking (45 min). Urine also was collected at time 0 and 24-hour urine collection was also taken to measure nicotine and cotinine excretion. Nicotine and cotinine were extracted from samples and assayed by gas chromatography. All data are presented as mean +/- SEM throughout the text, Tables and Figures unless indicated otherwise. RESULTS: Plasma nicotine levels rose from 1.11 +/- 0.62 ng/ml at baseline to a maximum of 60.31 +/- 7.58 ng/ml (p < 0.001) at the end of smoking (45 min). Plasma cotinine levels increased from 0.79 +/- 0.79 ng/ml at baseline to its highest concentration of 51.95 +/- 13.58 ng/ml (p < 0.001) 3 hours following the end of smoking. Saliva nicotine levels significantly rose from 1.05 +/- 0.72 to 624.74 +/- 149.3 ng/ml and also saliva cotinine levels significantly increased from 0.79 +/- 0.79 ng/ml to 283.49 +/- 75.04 ng/ml. Mean amounts of nicotine and cotinine excreted in urine during the 24-hour urine collection following smoking were equal to 73.59 +/- 18.28 and 249 +/- 54.78 microg, respectively. CONCLUSION: Following a single run of HB smoking, plasma, saliva and urinary nicotine and cotinine concentration increased to high values. This observation suggests that HB may not be an innocent habit, as people believe.