Unpredictability of an unconditioned stimulus (US) typically produces context conditioning in animals and humans. We modified the Martians task--a computer game measuring learning of Pavlovian associations through conditioned suppression--for assessing context conditioning in humans. One between-subjects and one within-subjects study are reported. Both experiments comprised four conditions: a predictable (Paired) condition in which the conditioned stimulus (CS) signaled the US, a neutral condition (No-US), one unpredictable condition in which the CS did not signal the US (Unpaired) and another one in which only unsignaled, temporally unpredictable USs were presented (US-only). Results showed more contextual conditioned suppression in the unpredictable conditions compared to the predictable condition. In contrast, more cued conditioned suppression occurred in the Paired condition than in the Unpaired condition. Consistent with animal research, context conditioning was increased by unpredictability. These data support the Martians task as a promising tool to extend research on human context conditioning. (Contains 5 figures.)