To show how to progress from the deviation of the visual axis (provided the diagnosis of concomitant strabismus is certain) to the classification of the squint in one out of the different squint syndromes and consequently to adopt the appropriate therapeutic strategy.Every sign correlated with the deviation contributes to progress step by step to the diagnosis of a given squint syndrome. The age on onset of strabismus, either convergent or divergent, and its characteristic, intermittent or constant, allow in a first step to evaluate the potential binocularity, as well in early as late (acquired) strabismus. The first group of early strabismus includes manifest infantile strabismus and microstrabismus. Both have abnormal binocularity. The possibility of functional amblyopia, angle variability and additional incomitances have to be investigated. Early intermittent strabismus keeping a potential normal binocularity are seldom. In the second group of late onset strabismus, retinal correspondence has to be investigated by correspondence tests and prism or bifocus compensation to distinguish between the two possible types (including the accommodative forms of strabismus), i.e. decompensated microstrabismus with abnormal binocularity or normosensorial strabismus with potential normal binocularity. In some cases potential binocularity may be initially uncertain and/or remain later on subnormal.As the result of this systematic approach, every cases of squint can be classified in one out of the different squint syndromes. Based on the precise diagnosis, the appropriate treatment can be carried out. The goals of treatment which can be reached in every syndrome are indicated.For an overall view of the squint syndromes a classification with two entrances are necessary, on the one hand early or late onset, on the other hand normal or abnormal binocular conditions.This approach of concomitant strabismus should serve as guide lines for clinical practice.