This contribution aims to clarify for exposure modellers and vulnerability and seismic risk assessors the basis on which seismic lateral loads have been established in all Yugoslavian seismic design codes since 1948. The particular focus is on JUS39/64 and JUS31/81 seismic design codes since they controlled the seismic safety of Macedonian (and Yugoslavian) exposure for 16 and 41 years, respectively. The analyses and discussions are centred on lateral force coefficients as a primary factor for representing the features of each design level. Presented is in all detail the developed K-Quotient method that efficiently compares inter-code lateral force levels. The method provides the closed solution for simplified lateral load calculation applicable to “stiff” buildings (T ≤ 0.5 s). The presented results are indicative of flexible buildings requiring further research on the subject.