The aim of this retrospective descriptive study was to describe both epidemiologically and clinically manifestations following severe scorpion envenomation and to define simple predictive factors which can be used in routine practice in general Intensive Care Units (ICU) as an indicator of poor prognosis. Cases were collected from hospital patients' files during 13-year (1990-2002) period in the medical Intensive Care Unit of a university hospital (Sfax - Tunisia). The diagnosis of scorpion envenomation was based on a history of scorpion sting. Nine hundred fifty-one patients, who were admitted for a scorpion sting, were analyzed. There were 769 patients (80.8%) in the grade III group (with cardiogenic shock and/or pulmonary edema or severe neurological manifestation (coma and/or convulsion)) and 182 patients (19.2%) in the grade II group (with systemic manifestations). Scorpion envenomation is more frequent in summer; indeed 82.3% of our patients were admitted between June and September. The mean age (+/-SD) was 14.7 +/- 17.4 years, ranging from 0.5 to 90 years. In this study 739 patients (77.8%) had neuromuscular signs, 700 patients (73.6%) had gastrointestinal signs and 585 patients (61.5%) had a pulmonary edema, while 195 patients (20.5%) had a cardiogenic shock. The mean blood sugar on admission was at 11.32 +/- 5.66 mmol/l, a high blood sugar level (>11 mmol/l) was observed in 39% of cases. The mean blood urea was at 7.1 +/- 3.2 mmol/l, it was above 10 mmol/l in 10.7% of cases. The mean of leucocytes was at 17 418 +/- 7833 cells/mm(3), it was above 11 000/mm(3) in 80% of cases. In the end of the stay in ICU, evolution was marked by the improvement of 879 patients (92.5%) while 72 patients (7.5%) died. A multivariate analysis found the following factors to be correlated with a poor outcome: age less than 5 years (OR = 2.27), fever >38.5 degrees C (OR = 2.79), coma with Glasgow coma score < or =8/15 (OR = 9.87), pulmonary edema (OR = 8.46), leucocytes >25 000 cells/mm3 (OR = 2.35) and blood urea >8 mmol/l (OR = 4.02). Moreover, in children group, a significant association was found between PRISM score and mortality rate, this model had a high discriminative power with an area under the ROC curve at 0.93. In the adult patients a significant association was found between SAPS II score and mortality rate, this model had a high discriminative power with an area under the ROC curve at 0.82. In summary, in severe scorpion envenomation, age less than 5 years, fever >38.5 degrees C, coma with Glasgow coma score < or =8/15, pulmonary edema, leucocytes >25 000 cells/mm3 and blood urea >8 mmol/l were associated with a poor outcome.