The first plasma in ASDEX Upgrade (AUG) was produced on 21stMarch '91 after more than 8 years of design, manufacture, and assembly. During the first operational period until August '92, with 1949 shots, the control and safety systems were commissioned in parallel with plasma discharges. Most discharges were run with He, but also H and D discharges were executed up to a plasma current of 800 kA at Bo = 2 T. With additional heating by ICRH, of up to 2.2 MW power and up to 2 s duration, the H-mode was obtained at a threshold of 1.2 MW after boronization. Discharges with line-densities of up to ne = 4*1019m−3and central electron temperatures of up to Teo =1.5 keV could adequately be diagnosed (ne-, Te-profiles, radiated power, ELM and MHD-activities, impurity influx …). With a CCD-camera the plasma boundary and critical in vessel components were observed. The magnetic diagnostics provided input for elaborate feedback control and reconstruction of the flux surfaces. The main effort of the experimental program was put on establishing the SN-divertor configuration, investigating the vertical n = 0 instability (VDE) and ICR heating scenarios. This paper describes the control systems, discharge essentials, vessel conditioning and the specific VDE behaviour.