Why you should always finish a course of antibiotics

This is especially true when dealing with STDs. Many patients stop taking antibiotics for their condition as soon as the condition seems to disappear. Not only is this a risk to themselves, but if can be an infected person appear perfectly normal to a possible sexual partner, leading to the spread of the disease. Worse, if the STD begins to mutate (develop resistance) towards the antibiotic, it could become silent, meaning that it has no immediate symptoms. If you don't finish taking the antibiotic, and the disease builds back up in your system, it will be much harder to diagnose and cure.

One point not mentioned in the above writeups

Antibiotics generally kill off the weak bacteria first. The tougher ones are more likely to die off with extra pummelling. That is why there is usually a ten day course to be followed. When the course is stopped early, the few and the strong multiply. ACK! It's the stronger variety that has been selected to continue on and make the rest of us miserable. What we have here is evolution on a microbial scale with an extra boost from antibiotic misuse.