Propagation of electromagnetic waves with orbital angular momentum (OAM) is investigated in indoor environments. The OAM modes generated by circular patch array antennas are used. With proper alignment and suppressed multipath, the OAM modes can transport multiple wireless data stream at the same time. Through measurements and ray-tracing simulations, it is found that the advantages of OAM modes are limited if those two conditions are not satisfied. It is also found that multipath effect can be enervated by using narrow beam antennas.