Tracking dogs follow a lost person's path from a starting point to where the person is. These dogs are able to seek lost people because they are trained to discriminate human scents. In other words, they don't seek for any human scent, but for one particular scent.

There are two main types of tracking tasks: wilderness search and urban search.

Urban tracking is usually more difficult for the dogs because the tracks have every kind of odors, including other people scent, pets scent and other scents. In addition, odors don't last long on artificial surfaces like pavement. And, as if it wasn't difficult enough, there could be lots of distractions while the dog is tracking: several people walking around, other pets nearby, etc.

On the other hand, wilderness search seems to be more amicable to dogs because tracks tend to have less people's scent and natural surfaces retains odors for longer time. In addition, natural surfaces could provide dogs with a potential second source of information: the contact or disturbance odor.

Since these dogs discriminate odors, they need two things to begin tracking:

- A starting point, also known as the Point Last Seen (PLS)

- An uncontaminated odor sample

The Point Last Seen (PLS) could be the last place where the lost person was actually seen or a place where that person was known to be. For instance, tracking can start in the place where the car of a person is, whether the person was seen there or not.

The uncontaminated odor sample is an article with the person's scent. Pillow covers and pajamas are great odor samples, but clothes and other articles could be useful. The most important thing is to keep the sample uncontaminated, so it must be handled with pincers and carried in Ziploc or brown paper bags (common waste bags are treated with chemicals to alter odors, so they are not useful for this task).

Usually, tracking dogs work on-leash (a 30-feet leash attached to a harness). However, on-leash work is not mandatory and some tracking dogs work off-leash.

Bloodhound is the preferred breed for tracking, though any dog can be trained to do this activity.

-- Tracking vs. trailing

Tracking and trailing dogs are not the same thing. The formers search with their nose to the ground while the latter combines that strategy with air scenting.

Nevertheless, both tracking and trailing dogs follow the path of a particular person (they discriminate scents). Thus, tracking and trailing dogs are used for the same purpose.

-- Scenting squashed insects

Contact odor is the odor (and perhaps some visual information) generated by environmental disturbance occurred while a person walks. For instance, scent of broken branches or squashed insects.

Although tracking dogs can't follow a path just by the contact odor, some experts suggest it could be a secondary source of information (maybe also visual information) under certain circumstances.