A study was carried out in Southern Italy on 90 Siriana breed goats with naturally occurring infections of gastrointestinal nematodes. Six similar groups of 15 goats were formed, one untreated control group and five groups treated once with ivermectin (I treatment) and once with netobimin (II treatment) at different times. Daily milk volume (mL) was recorded fortnightly for each animal for the whole lactation period. All the treated groups showed a total milk production that was statistically higher than that of the control group, and four of these groups showed at least one fortnightly measurement in which differences from the corresponding values of the control group were statistically significant. The best treatment timing seemed to be October-May, followed by February-June, December-May, and February-May.