OBJECTIVE To review the clinical and microbiological profile in patients with contact lens-related microbial keratitis (CLRMK). METHODS Hospital records of 435 patients with a diagnosis of microbial keratitis seen at Ramathibodi Hospital from January 1998 to December 2002 were retrospectively reviewed. All patients with CLRMK were included in the present study. RESULTS Of the 435 cases, 81 (18.6%) were related to contact lens use. The disposable or frequent replacement of lenses were the most common lens-wearing type. Thirty-four percent of patients did not practice proper contact lens care and 67% wore contact lenses overnight. Corneal cultures were performed in 58 of 81 cases (72%) and were positive in 42 of 58 cases (72%). Pseudomonas aeruginosa was the most common organism (59%), followed by Klebsiella pneumoniae (11%). Polymicrobial infection was found in 19 cases. Most of the patients responded to medical treatment that led to the healing of ulcers whereas four patients required therapeutic penetrating keratoplasty. Most, of the organisms were sensitive to antibiotics. After treatment, 43% of the patients have continued contact lenses-wearing. CONCLUSIONS CLRMK remains an essential problem in Thailand. Soft contact lens wear and overnight wearing seem to be the most important risk factors. Although the treatment outcome with medical therapy is good, keratitits may result in loss of vision. Ophthalmologist should warn contact lens wearers of this potential problem and instruct them on how to care for their lenses.