Background: The system of Blaschko's lines has been insufficiently documented on the head and neck. Objective: The aim of the study was to elaborate this pattern in a comprehensive way. Method: One hundred eighty-six figures showing skin lesions following Blaschko's lines on the head and neck were collected from literature and patient files, transposed into drawings, and subsequently categorized according to 3 standard perspectives. Transparent sheets were superimposed to delineate an archetypical pattern. Results: The definite lines are presented in a frontal, lateral, and dorsal view. On the face they show an hourglass-like configuration converging on the nasal root. However, in several areas these lines intersect at an angle of almost 90°. On the scalp they form a spiral configuration. Conclusion: The system of Blaschko's lines on the head and neck as elaborated by this study is more precise than previously published diagrams. Remarkably, this archetypical pattern shows definite crossing of lines. (J Am Acad Dermatol 2001;44:612-5.)