OBJECTIVE:Evaluation of several factors that affected the outcome in patients who underwent cochlear implant surgery. MATERIALS and METHODS:Retrospective study on 8 postlingual adults and 52 prelingual children with severe to profound hearing loss who underwent cochlear implantation at the Otolaryngology-Head and Neck surgery department, Kasr-Al Aini Hospital, Cairo University. A statistical analysis of several factors was performed to reveal any significant effect of the outcome of the procedure. RESULTS:The duration of deafness in adults showed a significant linear yet non-monotonic correlation with the postoperative average auditory thresholds as revealed by Pearson's correlation coefficient (r=0.839, p=0.009) and a linear regression model (f=14.211, p=0.009), which showed that the increase in the duration of deafness led to an increase in hearing thresholds and accounted for 70.3% of the variance in the outcome (β=0.839, t=3.770, and p=0.009). Age at implantation in children showed a positive linear, monotonic relation with the postoperative receptive (r=0.725, p<0.001, r S =0.354, p=0.010) and was a significant predictor of outcome (β=0.440, t=2.961; p=0.005) according to multiple linear regression. Mann-Whitney U-test was performed to evaluate the difference in medians of outcomes in relation to the regularity of attendance to speech rehabilitation. We found a significant effect over the auditory hearing thresholds (the mean ranks of regulars and irregulars were 21. 48 and 31.92, respectively; u=202.00, z=2.48, p<0.05) CONCLUSION: An increase in the duration of deafness leads to less favorable results of postoperative auditory thresholds in postlingual adults. Additionally, an increase in age at implantation may be associated with increased expressive language age in the first year postimplantation, and regular attendance to a speech rehabilitation program is associated with better postoperative auditory thresholds and a higher receptive language age.