Two-proton radioactivity was predicted more than 40 years ago. According to recent theoretical predictions, proton drip-line nuclei in the A=40–55 region were identified as the most promising candidates. The recent observation of two-proton radioactivity of 45Fe confirmed these predictions nicely. In the present paper, we will summarize experimental results for the decay of 45Fe, which include data from the 2002 discovery of this radcioactivity, but also new data. In addition, we will report on the first observation of 54Zn and its decay by two-proton radioactivity, the second case of this new decay mode. Finally, we will discuss tentative evidence for a small two-proton radioactivity branch for 48Ni. These experimental results are confronted to modern theories which succeed in describing reasonably well this decay mode.