Lost circulation has plagued the industry since the beginning of drilling. Severity of losses has been categorized based on the amount of barrels lost to the formation, i.e., Seepage, partial and total losses. This strategy doesn’t help understand the underlying drive mechanisms for losses and doesn’t provide enough data to propose a solution. The recently followed approach is focused on the lost-circulation mechanism based on the properties of the exposed formation: theses classifications are losses due to 1) Pore throats, 2) Induced or natural fractures, 3) Caverns. Lost circulation not only causes the adverse effect on mud loss itself, it can also lead to sever other issues, such as formation damage, stuck pipe, hole collapse and well control incidents. The current industry trend is moving towards drilling more low-pressure Zones, either through Depleted zones or Offshore, and lost circulation planning becoming vital to these projects. Knowledge of the type and the expected amount of mud loss can assist engineers to select the most appropriate and effective solution pre-plan accordingly. Moreover, it provides criteria to evaluate the effectiveness of the applied lost circulation technique. The objective of this thesis is to evaluate and compare the performance of different lost circulation materials (LCMs) to determine the effect of particle size distribution “PSD”, concentration and type on their performance to provide more wellbore strength and mitigate loss circulation. This thesis will first walk through the different lost circulation mechanisms and will explain the well strengthening practice with its different adopted techniques using LCMs and will point out the impact they have on the drilling process in order to reduce the chances of getting loss of circulation and consequently mitigate the non-productive time and overall cost. The last part of this work is specified to present the successful results of a case study. The main objectives of presenting this case study were to highlight the impact LCMs have on alleviating and suppressing loss of circulation and to present the resultant cost savings achieved when implying LCMs in the mud systems as a combating solution to mitigate the losses.