Background Minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) has been successfully used to treat degenerative diseases of the lumbar spine.There are few reports comparing the complications and clinical outcomes in older patients who have undergone one- or two-level MIS-TLIF with those of younger patients.The aim of this study was to investigate the clinical outcomes of MIS-TLIF in the treatment of degenerative disc disease of lumbar spine of the patients older than 65 years,with an emphasis on perioperative complications compared to the younger patients.Methods One hundred and fifty-one consecutive cases of one- or two-level degenerative disc disease of lumbar spine treated with MIS-TLIF were reviewed for the radiological and clinical outcomes.They were divided into elderly group (age ≥65 years old) and younger group (age ＜65 years old),and were followed for at least 6 months.Radiographs were obtained before and after surgery,3 months postoperatively,and at the final follow-up to determine the presence of fusion,hardware-related problems.The clinical outcomes were evaluated using the Oswestry Disability Index (ODI)before and after surgery,and at the final follow-up.The visual analogue scale (VAS) score of back and leg pain were evaluated as well.The intra-operative data and peri-operative complications were recorded.Results The mean age of these patients at operation was (57.7±14.2) years (range 26-82 years).Of 151 patients,62were 65 years or older.The elderly patients had more comorbidities and more porportion of lumbar canal stenosis.The overall fusion rate was 88.4％ at the final follow-up,with no significant difference between younger and elderly patients.The ODI,the VAS of back pain and radicular pain of both young and elderly group were significantly improved aftersurgery and at the final follow-up,without significant difference between two groups.There were 16 complications with an incidence of 10.6％,including 7 major complications and 9 minor complications.There was no significant difference of the incidence of complications between two groups.The incidence of dura tear was significantly related to bilateral deompression.Conclusions The clinical and radiological outcomes of MIS-TLIF in the treatment of one- or two-level degenerative disc diseases of lumbar spine in the elderly patients were satisfactory.Though there are more pre-operative comorbidities,with proper patient selection,the elderly patients are not at increased risk of perioperative complications compared to younger patients.Screw malposition and dura tear,which are the most frequent complications,were more related to the surgical technique and should be avoided.