Synthetic transmit aperture (STA) imaging has previously been investigated and compared to traditional imaging techniques in simulations and phantom studies. However, a full in-vivo study evaluating its clinical potential has yet to be conducted. This paper presents a preliminary in-vivo study of STA imaging in comparison to conventional imaging. The purpose is to evaluate whether STA imaging is feasible in-vivo, and whether the image quality obtained is comparable to traditional scanned imaging in terms of penetration depth, spatial resolution, contrast resolution, and artifacts. Acquisition was done using our RASMUS research scanner and a 5.5 MHz convex array transducer. STA imaging applies spherical wave emulation using multi-element subapertures and a 20 µs linear FM signal as excitation pulse. For conventional imaging a 64 element aperture was used in transmit and receive with a 1.5 cycle sinusoid excitation pulse. Conventional and STA images were acquired interleaved yielding ensuring exact same anatomical location. Image sequences were recorded in real-time, and processing was done offline. Male volunteers were scanned abdominally, and resulting images were compared by medical doctors using randomized blinded presentation. Penetration and image quality were scored and evaluated statistically. Results show that in-vivo imaging using STA imaging is feasible with improved image quality compared to conventional imaging.