The Rock-Eval technique in the last few decades has found extensive application for source rock analysis. The impact of shale particle crush-size and sample weight on key Rock-Eval mea-surements, viz. the S2 curve (heavier hydrocarbons released during the non-isothermal pyrolysis-stage) and the S4 curve (CO2 released from oxidation of organic matter during the oxidation-stage) are investi-gated in this study. For high and low total organic carbon (TOC) samples of different thermal maturity levels, it is apparent that particle crush-size has a strong influence on the results obtained from Rock-Eval analysis, with the effect being stronger in high-TOC samples. In comparison to the coarser-splits, S2 and pyrolyzable carbon (PC) were found to be higher for the finer crush sizes in all the shales stud-ied. The S4CO2 oxidation curve shapes of Permian shales show contrasting signatures in comparison to the Paleocene-aged lignitic shale, both from Indian basins. A reduced TOC was observed with rising sample weight for a mature Permian shale from the Jharia basin, while the other shales sampled showed no significant reduction. The results indicate that the S4CO2 curve and the S4Tpeak, are strongly dependent on the type of organic-matter present and its level of thermal maturity. Sample weight and particle size both influence the S2-curve shapes at different heating rates. With increasing sample weights, an increase in S2-curve magnitude was observed for the shales of diverse maturities. These dif-ferences in the S2 curve shape lead to substantially different kinetic distributions being fitted to these curves. These findings are considered to have significant implications for the accuracy of reaction kinet-ics obtained from pyrolysis experiments using different sample characteristics.