Eleven types/classes of compound with antifilarial activity were comparatively evaluated in Mastomys coucha infected with Litomosoides carinii, Acanthocheilonema viteae, Brugia malayi or B. pahangi. The paper deals with the efficacy of (i) predominantly microfilaricidal compounds [diethylcarbamazine, levamisole, avermectins (ivermectin, milbemycin), nitrofurans (nitrofurantoin, hydroxymethylnitrofurantoin, nifurtimox, furazolidone, furapyrimidone), organophosphorals (metrifonate, haloxon), and aminophenyl-amidines], (ii) predominantly macrofilaricidal compounds [suramin, benzimidazoles (flubendazole, mebendazole, oxfendazole, ciclobendazole, albendazole, cambendazole, fenbendazole), and arsenicals (thiacetarsamide, Mel PH, R7/45)], and (iii) micro- and macrofilaricidal compounds [benzazole derivatives (CGP 20376 and other benzothiazoles) and nitrophenylamines (amoscanate, CGP 6140)]. Minimum effective doses against microfilariae and minimum curative doses against adult filariae as well as detailed data on dose-efficacy relationships are reported for the various drugs. The results obtained in M. coucha are compared with those published for other experimental in vivo filarial systems, thus attempting to describe a general status of in vivo antifilarial activity of the compounds.