Background: Lap examination of the liver is used as an elective procedure to stage chronic liver diseases and intra-abdominal neoplasias. Hemodynamic variations in pulse(P), blood pressure(BP), and oxygen saturation(O 2 sat), are expected during minimally invasive surgical procedures using CS. The extension of these changes during Lap and their clinical significance remain unclear. AIM: Evaluate hemodynamic variations during Lap, and the correlation of Lap findings with liver histology(Hx). Patients and Methods: Pts undergoing Lap were prospectively evaluated from January to November 99. Lap was performed in the GI station using CS with meperidine and midazolam. Pneumoperitoneum was created using nitrous oxide. Pts received O 2 via nasal cannula 2L/min. P, BP and O 2 sat were recorded pre, intra and at the end of the Lap. Post-Lap monitoring was performed for 1 hour in the GI suite. Pts were then admitted for 23-hour observation. Results: 75 males, 53 females, mean age 55 (27-84) were studied. Lap indications: HCV in 65, staging cancer in 28, abnormal liver chemistries in 7, AIH in 6, liver masses in 6, PBC in 5, HBV in 4, cryptogenic cirrhosis in 3, NASH in 2, polycystic disease in 1, and granulomatous hepatitis in 1; 36 pts had platelet count 3 . All pts had normal prothrombin time. Biopsies were performed in 93pts. Lap findings: irregular surface in 39, cholestasis in 5, cirrhosis in 31, normal liver in 48, polycystic liver in 1 and liver metastasis in 4. The mean Lap duration was 32 minutes (14-74 min). Mean meperidine and midazolam doses were 56mg (0-150) and 2.8mg (0-13) respectively. No significant changes were observed in diastolic BP or O 2 sat. The systolic BP decreased from 141 pre- Lap to 136 mmHg post-Lap (p=0.00039). P significantly increased from 74 pre-Lap to 79 bpm end-Lap (p=0.000003). Systolic BP and P changes returned to baseline in the first hour post-Lap. There were no complications. All pts were discharged within 24 hours. Lap liver surface findings correlated with Hx fibrosis (p=0.00093) and detected 9 pts with cirrhosis not diagnosed by Hx. Conclusion: A mild but statistically significant decrease in systolic blood pressure and increase in pulse were observed during Lap. These hemodynamic changes returned to baseline within 1 hour post-Lap. Lap findings correlated with histologic fibrosis and increased the detection of cirrhosis. Lap using conscious sedation is safe and effective in the diagnosis of liver diseases.