Transdermal drug delivery systems (TDDS) are topically administered medicaments. Transdermal drug delivery is defined as a self-contained discrete dosage form, which when applied to the intact skin, will deliver the drug at a controlled rate to the systemic circulation. Transdermal patches are pharmaceutical preparation of varying sizes, containing, one or more active ingredient, intended to be applied to the unbroken skin in order to deliver the active ingredient to the systemic circulation after passing through the skin barriers. Compared to oral or systemic dosage systems, TDDS can offer a controlled release of the drugs through the skin into the patients, which could reduce the first-pass metabolism effects, lessen systemic side effects, improve the dosage efficacy by enabling steadier blood drug profiles throughout the treatment, and enhance patient compliance. Through a diffusion process, the drug enters the bloodstream directly though the skin. Since there is high concentration on the patch and low concentration in the blood, the drug will keep diffusing into the blood, the drug will keep diffusing into the blood for a long period of time, maintaining the constant concentration of drug in the blood flow. Characterization of transdermal patch is used to check it's quality, size, time of onset & duration, adhesive property, thickness, weight of patch, moisture content, uniformity & cutaneous toxicological studies. The present poster discusses the methods of preparation, characterization and applications of transdermal patches.