Aim: to assess the efficacy of the S.T.O.N.E stone scoring system to predict outcomes of post-operative complications and stone-free rates post PCNL for renal stones. Methods: It was a prospective study that was done on a total of 45 patients to follow the effect of stone characters presented by S.T.O.N.E score as a variable on outcomes and prognosis of PCNL. The study was carried out by experienced professors of urology at both Suez Canal University Hospitals and Nasser Institute for Research and Treatment in Cairo, on patients > 18 years old who were undergone single tract PCNL for primary renal stone and had pre-operative (NCCT). Results:show a statistically significant relation between complications occurrence and score complexity, data showed complications occurred at high score complexity in 19 cases, of all 22 cases with high complex score.16 cases of a total 21 of with moderate complex scores had complications, and one case of two with low complex scores had complications. Analysis of data showed a highly significant statistical relation between total nephrolithometric stone score and total operative time and fluoroscopy exposure time in the operation room. Conclusion: The present study investigated the effectiveness of the S.T.O.N.E. scoring system in predicting perioperative and postoperative complications and other operative parameters. S.T.O.N.E. scoring system can provide a more accurate prediction of success rates and possible complications of PCNL as it enrolls variables that are found to be highly effective in outcomes, however, these variables were neglected by other scoring systems, this score was also valid for staghorn calculi.