Three isolates of Andean potato latent virus (APLV) (Caj, Hu, Ay) each infected twenty‐seven species of plants in the families Amaranthaceae, Chenopodiaceae, Cucurbitaceae and Solanaceae but differed somewhat in the symptoms they induced. Nicotiana bigelovii and N. clevelandii proved the most useful diagnostic hosts. Symptoms were sometimes produced by all three isolates in cultivated and wild potatoes. In sap from systemically infected N. bigelovii and N. clevelandii leaves, all three isolates remained infective when diluted to 10‐6 and when stored at room temperature for at least 3 wk. The thermal inactivation points were 65–70 °C for Hu and Ay, but 75–80 °C for Caj. All three isolates differed serologically from Col, the original isolate of APLV, forming spurs in gel diffusion tests. No serological difference was found between Hu and Ay, but both formed spurs in reciprocal reactions with Caj. The data from light absorption, particle morphology and protein molecular weight for Caj, Hu and Ay are similar to those reported for other tymoviruses. APLV was found widespread in Andean countries. Copyright © 1977, Wiley Blackwell. All rights reserved