Online advertisers use multiple channels to reach consumers on the Internet. However, little is known on the interplay between online advertising channels. To fill this gap, this study provides a comprehensive overview of interaction effects in online advertising for individual consumers, including not only site visits, but also exposures that do not directly lead to a click. Based on a large cookie-based individual-level data set the authors analyze interaction effects within and between channel groups on purchase behavior. By classifying online marketing channels along the dimensions of initiation locus and previous brand awareness, they find significant interactions between contacts within and across channel types. While clicks following contacts in customer-initiated channels that require brand awareness overall have a negative effect on purchase propensity, previous clicks in firm-initiated channels positively interact with clicks in customer-initiated channels. The results can help managers to coordinate marketing strategies, optimize campaigns, and develop individualized marketing and targeting approaches.