Detached, semidetached, and contact eclipsing binaries are studied. For periodic systems, findings on U Oph, AK Her, SW Lao, and RT Per are reviewed and it is observed that AK Her is a double sinusoid pointing to the existence of four bodies. Two interpretations of the period changes in the star are presented. For a number of secular systems, O-C diagrams are interpreted and it is argued that the commonly assumed mechanisms of mass-exchange and mass-loss may not account for the variations of period in all cases, and that light time effect due to the presence of additional components could be another common cause for such variations. Estimated masses for third components from secular period changes are presented, along with circular third body orbit representations for secular systems. Peculiar systems are briefly discussed,and it is noted that in W UMa, the O-C diagram indicates a discontinuity in 1964 which coincides remarkably withthe flare observed in that system at the time.