If a house is not occupied by a planet at the time of birth, it is termed an Empty House. An absence of a planet does not necessarily mean that this particular area of life is unimportant to us, and can uncover almost as much about a person as occupied houses.
We know that planets in the houses signify areas of influence, good and bad, but a lack of planets indicates an area that does not require our attention until some later point in our lives when it is visited by a transiting planet.
For example, an unoccupied eleventh house indicates the need for a few close friends rather than a fondness for group activities. An unoccupied second house is usually less concerned about material matters than someone who has planets in this area.
Empty houses also relate to latent karma, suggesting that the area of life represented is not a required lesson within the present lifetime. Lots of empty houses in a birthchart indicate an old soul who has returned to earth in order to concentrate on one or two specific areas of life; this would reveal itself as the area where most of the planets are situated.