The relatively simple chromatophore system of the squid, Lolliguncula brevis, was studied with combined behavioural, morphological and electrophysiological methods in order to understand how the chromatophore patterns in the skin are organized at the level of the posterior chromatophore lobes (PCL). There are nine simple chromatic components of patterning in L. brevis. Retrograde transport of horseradish-peroxidase from chromatophores in the mantle skin established that the chromatophore motoneurones are located in the PCL. Focal threshold stimulation of the PCL in perfused, semi-intact preparations showed that the motor fields of individual chromatophore motoneurones are compact, including 2-60 chromatophores, generally of the same colour. Adjacent motoneurones in the lobe do not necessarily have adjacent motor fields in the skin.