OBJECTIVE The aim was to study the outcomes and results of therapeutic penetrating keratoplasty (Th PK) at a tertiary eye care hospital in northern India. METHODS In this retrospective interventional study, a cohort of 506 eyes that underwent a Th PK for microbial keratitis was evaluated. Th PK was performed in cases of recalcitrant microbial keratitis with impending perforation (descemetocele formation) or perforation (>3 mm). Medical records were reviewed for demographic details, risk factors, ulcer and perforation size, microbiological investigations, size of donor and recipient beds, postoperative complications, and anatomical and visual outcomes. RESULTS Anatomical success was seen in 454 eyes (89.7%). Preoperatively, the corrected distance visual acuity was <3/60 in 495 eyes (97.8%); after performing the Th PK, the corrected distance visual acuity was <3/60 in 249 eyes (49.2%), 3/60 to 6/60 in 182 eyes (35.9%), and >6/60 in 75 eyes (14.8%). Eyes with smaller grafts (<9 mm) had better anatomical and visual outcomes compared with eyes with larger grafts (9-11 mm; P = 0.03 and >11 mm; P = 0.0). A higher success rate was achieved with pure bacterial or fungal organisms rather than with mixed infections. A higher incidence of secondary glaucoma was seen in eyes with perforated ulcers (29.36%; 111/378) than in eyes without perforation (11.71%; 15/128) (P <.01) and in eyes with larger graft sizes (>11 mm and 9-11 mm) than in eyes with smaller graft sizes (<9 mm) (P <0.01). CONCLUSIONS Th PK has a definitive role in the management of severe and refractory keratitis with a high success in restoring anatomical integrity and providing useful vision. Better outcomes may be achieved with early intervention before perforation or limbal/scleral extension.