Two Algol-type eclipsing binary systems (EW Lyr and IV Cas) have been investigated for period changes. Our study was primarily focused on the light-time effect with an alternative explanation by magnetic activity cycles. In the case of EW Lyr we have found a third body in the orbit with a period of about 78 years, an amplitude A=0.052 days and orbital eccentricity e=0.57. For IV Cas the long period is 58 years, amplitude A=0.034 days and zero eccentricity. With these results we are also able to calculate mass functions and minimal masses of these components.