There are two ways in which translators can exercise control over machine translation systems. If it's a rule-based system, they can adapt existing dictionaries or create new ones in order to deal with new subject domains or new usage. Then, whether the system is rule-based or statistical, they can evaluate whether it's fit for its intended purpose. Time and resources permitting, workshop participants will have the opportunity to carry out both types of exercise. The first aims to improve the MT system, while the second will introduce a number of more or less reliable techniques for assessing the scale of the improvement.