This paper presents a systematic methodology to create customized structural macromodels for a specific analog circuit. The novel contributions of the method include definition of the building block behavioral concept and two original algorithms to generate structural models. Experiments are offered for two-stage opamp and operational transconductor amplifier (OTA) circuits. The automatically produced models are accurate, offer design insight, and require low modeling effort. Categories and Subject Descriptors I.6.5 [Model Development]: Modeling methodologies General Terms Algorithms, Design Keywords Analog circuits, Structural macromodel