When the Board of Directors of the Belgian Ophthalmological Soci­ ety, in its session of November 26th 1978, asked me to prepare a report on strabismus to be presented at the joint meeting of the Dutch and Belgian Ophthalmological Societies to be held on June 13th 1981, I felt greatly honored but still more overwhelmed by the immensity of the task. I took advantage of the complete liberty given to me by the Board of Directors, first to limit the work to one particular form of strabismus, i.e. the convergent comitant form; second, to seek the help of what I thought to be the best strabologists in the Low Countries; third, to aim not at an encyclopedic treatise but at a practical volume destined to the general ophthalmologist. This volume is thus limited to the various aspects of convergent strabismus, more accurately of comitant convergent strabismus. The omission of the word" comitant" is purposely made to avoid the dif­ fic'ulties accompanying the explanation of this term and all the acroba­ tics needed to explain that most comitant strabismus are not complete­ ly comitant. The choice of this particular form of strabismus seems logical. First of all, it is the most common form of strabismus. On the other hand, most principles concerning examination and treatment can with some modifications be applied to other forms of strabismus.