Detectability plays a major role in estimating lizard populations. Here a new method is presented, with which estimations can be made on the numbers of common lizards and sand lizards. It is based on the numbers seen per man hour in a certain type of terrain, at a certain hour of the day in a certain period of the year and of course in a certain type of weather. With this method repeatable figures can be obtained when carried out in certain hours in the months of April, May and early June and in a part of September, for the sand lizard even in some hours of July and August.