To solve this problem first find out why they became close, you appreciate what you have, decide what you want to achieve and then start to fix the problem.
The most common reasons for reducing size of pants: the shrinkage of fabric after washing, increase of volume of the body, the thing bought in a hurry or to lose weight. At this stage, determine the composition of the tissue, based on it, consider whether this fabric to stretch more than it is. If it's jeans, leather trousers or pants stretching tissues, and then safely handle the job.
Assessing the situation, think about how much you want to stretch pants: just to button up the pants to sit down, or to feel comfortable in well-fitting pants.
Many manufacturers suggest to walk around in wet pants, so they are a bit stretched. So wet your pants, put them on and walk around in them for a while.
If you want to stretch leather pants, use soap, Cologne or a special tool for stretching the skin, and finally treat the pants with glycerin, so that they shone like new.
Your trousers don't fasten on you? Then let more slender girlfriend to wear them for a while. Very often the pants will stretch during wear.
They say that at the end of the day our bodies become more as after a meal. Try to put your pants in the morning and wear them for some time, quite possibly in a few days they'll be a little more.
If all of the above does not help, it makes sense to sell the pants, to buy or to sew a new, larger size. The need for stretching the pants can fall by itself, if you try to change the system of power and to lose a couple pounds.