The authors examined serologically 353 clinically healthy persons in 5 localities in South Columbia for leptospirosis using the MAL-reaction with 15 serovars of 15 serogroups. The positivity was high - 18.4% namely with the serovars of the serogroups Icterohaemorrhagiae, Canicola, Pyrogenes, Australis, Pomona, Grippotyphosa, Sejroe, Hebdomadis, Bataviae, Panama and Shermani. Sera reacted positive in titer levels of 1:400 and higher only with the serovars of the serogroups Icterohaemorrhagiae, Canicola, Australis, Grippotyphosa, Sejroe, Hebdomadis, Panama and Shermani. In the total positivity were the serovars of the serogroups Icterohaemorrhagiae with 30.8%, Grippotyphosa with 23.1%, Australis with 15.4%, Panama and Pyrogenes with 10.8% each, Pomona with 6.2%, Shermani with 4.6% and Canicola, Sejroe, Hebdomadis, Bataviae with 3.1% each. The high positivity of the sera from the Mocoa for L.grippotyphosa was surprising - 20.7%.