摘要： Purpose To study the impact of stone density as assessed by Hounsfield units (HU) on total laser energy (TLE) used and total laser time (TLT) spent in complete fragmentation of upper urinary tract stones. In addition, we also studied the impact of stone composition on the laser energy and time required for fragmentation. Methods Thirty consecutive patients fulfilling inclusion and exclusion criteria were included in the study. Patients with renal or proximal ureteral stones with a size of 5–20?mm were included. Stone fragmentation was performed using Ho:YAG 100?W laser and TLT and TLE were correlated with the HU and stone composition. Results The mean stone diameter was 10.83 ± 3.5?mm and the mean HU was 893 ± 315. The mean TLE and TLT were 8.86 ± 3.12?kJ and 18.46 ± 6.9?min, respectively. We observed a strong positive correlation between HU and TLE (r = 0.84, p value < 0.001) and between HU and TLT (r = 0.58, p value = 0.001). However, the stone composition did not influence the lasering energy (p value = 0.36) and lasering time (p value = 0.30). Stone diameter also had significant positive correlation with TLE (r = 0.41; p = 0.02) and TLT (r = 0.54; p? 0.002). When controlling for stone size the correlation of HU with TLE (r = 0.83; p < 0.001) and TLT (r = 0.52; p = 0.004) remained significant. Conclusions HU and stone diameter are significant predictors of TLE and TLT when using Ho:YAG laser for stone fragmentation. However, stone composition and stone location failed to show any significant effect on either of these parameters.