Selective logging is the primary driver of forest degradation in the tropics and reduces the 26 capacity of forests to harbour biodiversity, maintain key ecosystem processes, sequester carbon, and 27 support human livelihoods. While the preceding decade has seen a tremendous improvement in the 28 ability to monitor forest disturbances from space, advances in forest monitoring have almost 29 universally relied on optical satellite data from the Landsat program, whose effectiveness is limited in 30 tropical regions with frequent cloud cover. Synthetic aperture radar (SAR) data can penetrate clouds 31 and have been utilized in forest mapping applications since the early 1990s, but no study has 32 exclusively used SAR data to map tropical selective logging. A detailed selective logging dataset from 33 three lowland tropical forest regions in the Brazilian Amazon was used to assess the effectiveness of 34 SAR data from Sentinel-1, RADARSAT-2 and PALSAR-2 for monitoring tropical selective logging. 35We built Random Forest models in an effort to classify pixel-based differences in logged and 36 unlogged areas. In addition, we used the BFAST algorithm to assess if a dense time series of Sentinel-37 1 imagery displayed recognizable shifts in pixel values after selective logging. Random Forest 38 classification with SAR data (Sentinel-1, RADARSAT-2, and ALOS-2 PALSAR-2) performed 39 poorly, having high commission and omission errors for logged observations. This suggests little to 40 no difference in pixel-based metrics between logged and unlogged areas for these sensors. In contrast, 41the Sentinel-1 time series analyses indicated that areas under higher intensity selective logging (> 20 42 m 3 ha -1 ) show a distinct spike in the number of pixels that included a breakpoint during the logging 43 season. BFAST detected breakpoints in 50% of logged pixels and exhibited a false alarm rate of 44 approximately 10% in unlogged forest. Overall our results suggest that SAR data can be used in time 45 series analyses to detect tropical selective logging at high intensity logging locations within the 46 Amazon (> 20 m 3 ha -1 ). These results have important implications for current and future abilities to 47 detect selective logging with freely available SAR data from SAOCOM 1A, the planned continuation 48 missions of Sentinel-1 (C and D), ALOS PALSAR-1 archives (expected to be opened for free access 49 in 2020), and the upcoming launch of NISAR. 50 51