Background: Health information system, as most other information systems, is devoted to management and decision-making. The purpose of any information system is to provide accurate and updated information for making decisions promptly. Decision-making is an integral part of medical profession. This was simplified with diagnostic and therapeutic algorithms. Objective: The purpose of this paper is to show the importance of algorithms in daily doctor practice. Great help is provided by diagnostic algorithms in setting the diagnosis and determining the treatment of a complex disease such as malignant melanoma. An algorithm is a procedure or formula for solving a problem. They simplify our work and through a series of logical steps lead to the ultimate goal as fast as possible - to diagnosis. Our goal is to show algorithms that we use in decision-making for diagnosis and treatment of malignant melanoma. Patients and methods: In retrospective study, we analyzed 96 patients who were treated at the Clinic for Plastic and Reconstructive Surgery in the period from January 1st 2005 to January 1st 2008, aged 19 to 82 years. In all patients, sentinel lymph node biopsy was performed with later pathohistology verification. We showed the results of analysis of patients with a diagnosis of malignant melanoma in a period of three years. Data was analyzed regarding sex, age, tumor location, histological type, level of invasion and frequency of metastasis in sentinel lymph node and in regional lymph nodes. Results: Analysis of patients by age groups showed that the largest number of patients was in the age group from 40 to 60 years of age (50% of patients). The largest number of patients had a superficial spreading melanoma, in 61%, and nodular melanoma in 32% of patients. The largest number of patients had level III (32%) and IV (30%) using Clark. In 40% of patients metastases were found in the sentinel lymph nodes. The results showed that the metastases in regional lymph nodes with positive sentinel lymph node was present in 47% of patients. Conclusion: Decision-making is an integral part of medical profession. This is facilitated with diagnostic and therapeutic algorithms. [Acta Inform Med 2008; 16(4.000): 188-190]

information system, algorithms, malignant melanoma