Wireless systems require increasingly large system bandwidths that are only available at millimeter-wave frequencies. Such spectrum bands offer the potential for multi-gigabit-per-second data rates to low-cost massively broadband® devices. To enable mobile outdoor millimeter-wave cellular-type applications, it is necessary to determine the coverage potential of base stations in real-world environments. This paper presents the results of a measurement campaign of 38 GHz outdoor urban cellular channels using directional antennas at both the mobile and the base station, and assesses outage probabilities at two separate transmitter locations on the campus of The University of Texas at Austin. Our measurements demonstrate the viability of directional antennas and site-specific planning for future mm-wave cellular, and show that cell radii of ∼ 200 M will provide a very high probability of coverage in an urban environment. As production costs for millimeter-wave technologies continue to fall , we envision millimeter-wave cellular systems with dense base station deployments as a cost effective means of delivering multi-Gbps data rates to mobile cell phone and internet users.