This study was carried out to investigate the stock market reaction for right issues anddebenture issues of Colombo Stock Exchange (CSE) during the period of 2013 to2017.Inabsence of seasonal equity issues in CSE, right issues have been considered as equity issuesand debenture issues have been considered as debt issues. During the sample period, 65right issue announcements and 30 debenture issue announcements were reported, fromwhich only 47 right issue and 20 debenture issue announcements were qualified for thesample. Study Methodology was used to investigate the ex-ante and expose marketreactions, for the two types of security announcements while predicting abnormal returns,based on three alternative normal/expected returns modeling methods. Namely MeanAdjusted Model, Market Adjusted Model, and Capital Asset Pricing Model, further, a crosssectional regression analysis was carried out to assess the factors affecting price reaction,around security issue announcements.For right issue announcements listed companies of CSE reacted positively during the 30days prior to the announcement and started to react negatively from 2 days after theannouncements according to all three methods utilized to generate abnormal returns.Though a cumulative abnormal return (CAAR) of the three-day event window is positive,the CAAR bfter Day 2 was significantly negative. Market reacted negatively during theperiod prior to debenture issues and continued to do so during the post event window aswell. Thdugh the non-zero CAAR on immediately around announcement day (day 1,0, +1)was not statistically significant, the negative returns of 30 days and 10 days pre and post tothe announcement were significant. Again, the direction of the price reaction was notsignificant. Though the magnitude and significance of abnormal return generated throughthree alternatives normal return modeling methods differs, the pattern of the CAAR of allthree models were similar, this confirms the previous findings on multiple model usage.Cross sectional regression analysis reveals a significant positive influence of issue size onprice reaction/abnormal returns of issuing firm and significant negative impact of pre offerleverage ratio on price reaction/abnormal returns of the issuing firm. Filially the analysisreveals that CSE is not efficient in semi strong form sense.