Medical Certificates come in different classes depending on the type of flying that you will be doing. If you are planning to be a Private pilot than all you will need is a Third Class Medical. A Third Class is good for 3 years if you are under 40 years old, and 2 years if you are over 40 years old. If you plan on making a career out of flying you will need to obtain a Second Class Medical before you can be hired, and eventually if you go to fly for an airline you will need a First Class Medical. The only major difference is the frequency of medical exams. First Class is good for 6 months, and Second Class is good for 1 year. Click here for a list of Portland area Medical Examiners.